Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $208.89   10.433%   $230.6835   $230.68   $230.70   $230.70  
  Purchase #2 $156.32   13.354%   $177.195   $177.20   $177.20   $177.20  
  Purchase #3 $141.49   9.856%   $155.4353   $155.44   $155.45   $155.40  
  Purchase #4 $210.56   11.181%   $234.1027   $234.10   $234.10   $234.10  
  Purchase #5 $159.77   8.701%   $173.6716   $173.67   $173.65   $173.70  
  Purchase #6 $232.41   3.683%   $240.9697   $240.97   $240.95   $241.00  
  Purchase #7 $181.52   12.821%   $204.7927   $204.79   $204.80   $204.80  
  7 purchase totals = $1,290.96       $1,416.8505   $1,416.85   $1,416.85   $1,416.90