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 $195.66   11.599%   $218.3546   $218.35   $218.35   $218.40  
  Purchase #2 $84.29   10.240%   $92.9213   $92.92   $92.90   $92.90  
  Purchase #3 $47.70   6.454%   $50.7786   $50.78   $50.80   $50.80  
  Purchase #4 $204.93   11.826%   $229.165   $229.17   $229.15   $229.20  
  Purchase #5 $97.55   4.326%   $101.77   $101.77   $101.75   $101.80  
  Purchase #6 $247.31   9.391%   $270.5349   $270.53   $270.55   $270.50  
  Purchase #7 $85.61   12.612%   $96.4071   $96.41   $96.40   $96.40  
  7 purchase totals = $963.05       $1,059.9315   $1,059.93   $1,059.90   $1,060.00