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 $47.86   8.693%   $52.0205   $52.02   $52.00   $52.00  
  Purchase #2 $180.46   6.764%   $192.6663   $192.67   $192.65   $192.70  
  Purchase #3 $71.62   7.596%   $77.0603   $77.06   $77.05   $77.10  
  Purchase #4 $158.30   9.547%   $173.4129   $173.41   $173.40   $173.40  
  Purchase #5 $208.28   11.566%   $232.3697   $232.37   $232.35   $232.40  
  Purchase #6 $197.71   3.520%   $204.6694   $204.67   $204.65   $204.70  
  Purchase #7 $189.42   13.438%   $214.8743   $214.87   $214.85   $214.90  
  7 purchase totals = $1,053.65       $1,147.0734   $1,147.07   $1,146.95   $1,147.20