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 $46.40   4.845%   $48.6481   $48.65   $48.65   $48.60  
  Purchase #2 $119.95   9.470%   $131.3093   $131.31   $131.30   $131.30  
  Purchase #3 $231.50   8.656%   $251.5386   $251.54   $251.55   $251.50  
  Purchase #4 $75.43   12.340%   $84.7381   $84.74   $84.75   $84.70  
  Purchase #5 $238.38   12.646%   $268.5255   $268.53   $268.55   $268.50  
  Purchase #6 $133.86   13.332%   $151.7062   $151.71   $151.70   $151.70  
  Purchase #7 $151.87   10.531%   $167.8634   $167.86   $167.85   $167.90  
  7 purchase totals = $997.39       $1,104.3292   $1,104.34   $1,104.35   $1,104.20