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 $97.67   13.804%   $111.1524   $111.15   $111.15   $111.20  
  Purchase #2 $185.75   4.517%   $194.1403   $194.14   $194.15   $194.10  
  Purchase #3 $241.97   4.593%   $253.0837   $253.08   $253.10   $253.10  
  Purchase #4 $48.49   10.223%   $53.4471   $53.45   $53.45   $53.40  
  Purchase #5 $45.95   7.629%   $49.4555   $49.46   $49.45   $49.50  
  Purchase #6 $30.52   4.857%   $32.0024   $32.00   $32.00   $32.00  
  Purchase #7 $59.43   7.217%   $63.7191   $63.72   $63.70   $63.70  
  7 purchase totals = $709.78       $757.0005   $757.00   $757.00   $757.00