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 $175.50   3.829%   $182.2199   $182.22   $182.20   $182.20  
  Purchase #2 $66.41   10.236%   $73.2077   $73.21   $73.20   $73.20  
  Purchase #3 $175.68   4.534%   $183.6453   $183.65   $183.65   $183.60  
  Purchase #4 $210.91   3.407%   $218.0957   $218.10   $218.10   $218.10  
  Purchase #5 $59.53   10.768%   $65.9402   $65.94   $65.95   $65.90  
  Purchase #6 $236.60   6.484%   $251.9411   $251.94   $251.95   $251.90  
  Purchase #7 $37.26   11.571%   $41.5714   $41.57   $41.55   $41.60  
  7 purchase totals = $961.89       $1,016.6213   $1,016.63   $1,016.60   $1,016.50