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 $33.46   10.466%   $36.9619   $36.96   $36.95   $37.00  
  Purchase #2 $188.50   7.362%   $202.3774   $202.38   $202.40   $202.40  
  Purchase #3 $214.50   9.217%   $234.2705   $234.27   $234.25   $234.30  
  Purchase #4 $73.26   7.130%   $78.4834   $78.48   $78.50   $78.50  
  Purchase #5 $149.90   6.685%   $159.9208   $159.92   $159.90   $159.90  
  Purchase #6 $205.97   10.362%   $227.3126   $227.31   $227.30   $227.30  
  Purchase #7 $151.39   5.230%   $159.3077   $159.31   $159.30   $159.30  
  7 purchase totals = $1,016.98       $1,098.6343   $1,098.63   $1,098.60   $1,098.70