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 $88.55   10.699%   $98.024   $98.02   $98.00   $98.00  
  Purchase #2 $102.55   7.865%   $110.6156   $110.62   $110.60   $110.60  
  Purchase #3 $188.94   8.822%   $205.6083   $205.61   $205.60   $205.60  
  Purchase #4 $218.78   8.359%   $237.0678   $237.07   $237.05   $237.10  
  Purchase #5 $121.35   3.532%   $125.6361   $125.64   $125.65   $125.60  
  Purchase #6 $19.25   7.315%   $20.6581   $20.66   $20.65   $20.70  
  Purchase #7 $202.55   11.717%   $226.2828   $226.28   $226.30   $226.30  
  7 purchase totals = $941.97       $1,023.8927   $1,023.90   $1,023.85   $1,023.90