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 $132.48   6.693%   $141.3469   $141.35   $141.35   $141.30  
  Purchase #2 $246.41   5.474%   $259.8985   $259.90   $259.90   $259.90  
  Purchase #3 $73.60   8.601%   $79.9303   $79.93   $79.95   $79.90  
  Purchase #4 $190.95   4.376%   $199.306   $199.31   $199.30   $199.30  
  Purchase #5 $141.71   12.610%   $159.5796   $159.58   $159.60   $159.60  
  Purchase #6 $148.40   13.451%   $168.3613   $168.36   $168.35   $168.40  
  Purchase #7 $135.39   5.783%   $143.2196   $143.22   $143.20   $143.20  
  7 purchase totals = $1,068.94       $1,151.6422   $1,151.65   $1,151.65   $1,151.60