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 $117.99   6.810%   $126.0251   $126.03   $126.05   $126.00  
  Purchase #2 $142.91   6.611%   $152.3578   $152.36   $152.35   $152.40  
  Purchase #3 $171.96   13.382%   $194.9717   $194.97   $194.95   $195.00  
  Purchase #4 $133.60   7.122%   $143.115   $143.12   $143.10   $143.10  
  Purchase #5 $5.75   5.426%   $6.062   $6.06   $6.05   $6.10  
  Purchase #6 $140.31   5.674%   $148.2712   $148.27   $148.25   $148.30  
  Purchase #7 $88.90   5.686%   $93.9549   $93.95   $93.95   $94.00  
  7 purchase totals = $801.42       $864.7577   $864.76   $864.70   $864.90