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 $95.85   11.821%   $107.1804   $107.18   $107.20   $107.20  
  Purchase #2 $203.62   10.702%   $225.4114   $225.41   $225.40   $225.40  
  Purchase #3 $115.44   7.398%   $123.9803   $123.98   $124.00   $124.00  
  Purchase #4 $142.27   6.499%   $151.5161   $151.52   $151.50   $151.50  
  Purchase #5 $245.70   4.428%   $256.5796   $256.58   $256.60   $256.60  
  Purchase #6 $151.32   5.115%   $159.06   $159.06   $159.05   $159.10  
  Purchase #7 $185.47   10.111%   $204.2229   $204.22   $204.20   $204.20  
  7 purchase totals = $1,139.67       $1,227.9507   $1,227.95   $1,227.95   $1,228.00