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 $69.35   10.828%   $76.8592   $76.86   $76.85   $76.90  
  Purchase #2 $243.61   13.453%   $276.3829   $276.38   $276.40   $276.40  
  Purchase #3 $212.97   13.286%   $241.2652   $241.27   $241.25   $241.30  
  Purchase #4 $213.72   9.860%   $234.7928   $234.79   $234.80   $234.80  
  Purchase #5 $125.57   5.228%   $132.1348   $132.13   $132.15   $132.10  
  Purchase #6 $237.98   7.464%   $255.7428   $255.74   $255.75   $255.70  
  Purchase #7 $53.69   11.846%   $60.0501   $60.05   $60.05   $60.10  
  7 purchase totals = $1,156.89       $1,277.2278   $1,277.22   $1,277.25   $1,277.30