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 $86.50   11.504%   $96.451   $96.45   $96.45   $96.50  
  Purchase #2 $29.86   12.283%   $33.5277   $33.53   $33.55   $33.50  
  Purchase #3 $12.58   13.549%   $14.2845   $14.28   $14.30   $14.30  
  Purchase #4 $63.79   3.344%   $65.9231   $65.92   $65.90   $65.90  
  Purchase #5 $207.49   12.286%   $232.9822   $232.98   $233.00   $233.00  
  Purchase #6 $155.92   12.549%   $175.4864   $175.49   $175.50   $175.50  
  Purchase #7 $116.58   6.793%   $124.4993   $124.50   $124.50   $124.50  
  7 purchase totals = $672.72       $743.1542   $743.15   $743.20   $743.20