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 $46.25   13.608%   $52.5437   $52.54   $52.55   $52.50  
  Purchase #2 $216.93   9.792%   $238.1718   $238.17   $238.15   $238.20  
  Purchase #3 $153.51   10.215%   $169.191   $169.19   $169.20   $169.20  
  Purchase #4 $220.85   12.862%   $249.2557   $249.26   $249.25   $249.30  
  Purchase #5 $235.62   4.869%   $247.0923   $247.09   $247.10   $247.10  
  Purchase #6 $245.46   9.509%   $268.8008   $268.80   $268.80   $268.80  
  Purchase #7 $175.73   13.643%   $199.7048   $199.70   $199.70   $199.70  
  7 purchase totals = $1,294.35       $1,424.7601   $1,424.75   $1,424.75   $1,424.80