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 $57.84   8.750%   $62.901   $62.90   $62.90   $62.90  
  Purchase #2 $249.32   13.273%   $282.4122   $282.41   $282.40   $282.40  
  Purchase #3 $105.83   4.681%   $110.7839   $110.78   $110.80   $110.80  
  Purchase #4 $60.50   6.192%   $64.2462   $64.25   $64.25   $64.20  
  Purchase #5 $180.85   3.168%   $186.5793   $186.58   $186.60   $186.60  
  Purchase #6 $199.39   9.491%   $218.3141   $218.31   $218.30   $218.30  
  Purchase #7 $5.88   13.674%   $6.684   $6.68   $6.70   $6.70  
  7 purchase totals = $859.61       $931.9207   $931.91   $931.95   $931.90