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 $87.41   7.642%   $94.0899   $94.09   $94.10   $94.10  
  Purchase #2 $107.53   10.765%   $119.1056   $119.11   $119.10   $119.10  
  Purchase #3 $40.30   5.510%   $42.5205   $42.52   $42.50   $42.50  
  Purchase #4 $211.81   11.273%   $235.6873   $235.69   $235.70   $235.70  
  Purchase #5 $129.76   11.832%   $145.1132   $145.11   $145.10   $145.10  
  Purchase #6 $212.88   5.739%   $225.0972   $225.10   $225.10   $225.10  
  Purchase #7 $22.38   4.418%   $23.3687   $23.37   $23.35   $23.40  
  7 purchase totals = $812.07       $884.9824   $884.99   $884.95   $885.00