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 $58.68   4.574%   $61.364   $61.36   $61.35   $61.40  
  Purchase #2 $87.41   9.162%   $95.4185   $95.42   $95.40   $95.40  
  Purchase #3 $87.44   7.373%   $93.887   $93.89   $93.90   $93.90  
  Purchase #4 $64.26   8.704%   $69.8532   $69.85   $69.85   $69.90  
  Purchase #5 $198.53   9.372%   $217.1362   $217.14   $217.15   $217.10  
  Purchase #6 $233.90   12.637%   $263.4579   $263.46   $263.45   $263.50  
  Purchase #7 $64.60   12.747%   $72.8346   $72.83   $72.85   $72.80  
  7 purchase totals = $794.82       $873.9514   $873.95   $873.95   $874.00