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 $68.57   10.851%   $76.0105   $76.01   $76.00   $76.00  
  Purchase #2 $214.39   9.275%   $234.2747   $234.27   $234.25   $234.30  
  Purchase #3 $65.89   6.804%   $70.3732   $70.37   $70.35   $70.40  
  Purchase #4 $116.34   4.111%   $121.1227   $121.12   $121.10   $121.10  
  Purchase #5 $212.56   3.429%   $219.8487   $219.85   $219.85   $219.80  
  Purchase #6 $226.67   10.139%   $249.6521   $249.65   $249.65   $249.70  
  Purchase #7 $217.79   12.464%   $244.9353   $244.94   $244.95   $244.90  
  7 purchase totals = $1,122.21       $1,216.2172   $1,216.21   $1,216.15   $1,216.20