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 $70.39   8.179%   $76.1472   $76.15   $76.15   $76.10  
  Purchase #2 $224.39   9.374%   $245.4243   $245.42   $245.40   $245.40  
  Purchase #3 $118.79   8.508%   $128.8967   $128.90   $128.90   $128.90  
  Purchase #4 $102.32   9.810%   $112.3576   $112.36   $112.35   $112.40  
  Purchase #5 $101.63   13.209%   $115.0543   $115.05   $115.05   $115.10  
  Purchase #6 $198.40   4.796%   $207.9153   $207.92   $207.90   $207.90  
  Purchase #7 $235.34   13.705%   $267.5933   $267.59   $267.60   $267.60  
  7 purchase totals = $1,051.26       $1,153.3887   $1,153.39   $1,153.35   $1,153.40