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 $215.99   8.372%   $234.0727   $234.07   $234.05   $234.10  
  Purchase #2 $225.30   4.474%   $235.3799   $235.38   $235.40   $235.40  
  Purchase #3 $206.74   8.406%   $224.1186   $224.12   $224.10   $224.10  
  Purchase #4 $69.69   5.137%   $73.27   $73.27   $73.25   $73.30  
  Purchase #5 $187.49   8.623%   $203.6573   $203.66   $203.65   $203.70  
  Purchase #6 $149.75   12.843%   $168.9824   $168.98   $169.00   $169.00  
  Purchase #7 $99.53   5.375%   $104.8797   $104.88   $104.90   $104.90  
  7 purchase totals = $1,154.49       $1,244.3606   $1,244.36   $1,244.35   $1,244.50