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 $184.34   13.523%   $209.2683   $209.27   $209.25   $209.30  
  Purchase #2 $102.93   8.571%   $111.7521   $111.75   $111.75   $111.80  
  Purchase #3 $71.59   4.240%   $74.6254   $74.63   $74.65   $74.60  
  Purchase #4 $241.71   7.823%   $260.619   $260.62   $260.60   $260.60  
  Purchase #5 $51.33   5.863%   $54.3395   $54.34   $54.35   $54.30  
  Purchase #6 $184.60   9.336%   $201.8343   $201.83   $201.85   $201.80  
  Purchase #7 $168.63   12.267%   $189.3158   $189.32   $189.30   $189.30  
  7 purchase totals = $1,005.13       $1,101.7544   $1,101.76   $1,101.75   $1,101.70