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 $41.37   6.172%   $43.9234   $43.92   $43.90   $43.90  
  Purchase #2 $232.55   9.683%   $255.0678   $255.07   $255.05   $255.10  
  Purchase #3 $119.71   11.208%   $133.1271   $133.13   $133.15   $133.10  
  Purchase #4 $240.65   11.728%   $268.8734   $268.87   $268.85   $268.90  
  Purchase #5 $234.94   6.126%   $249.3324   $249.33   $249.35   $249.30  
  Purchase #6 $9.68   8.836%   $10.5353   $10.54   $10.55   $10.50  
  Purchase #7 $124.43   8.700%   $135.2554   $135.26   $135.25   $135.30  
  7 purchase totals = $1,003.33       $1,096.1148   $1,096.12   $1,096.10   $1,096.10