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 $108.73   9.675%   $119.2496   $119.25   $119.25   $119.20  
  Purchase #2 $13.52   3.802%   $14.034   $14.03   $14.05   $14.00  
  Purchase #3 $173.90   12.495%   $195.6288   $195.63   $195.65   $195.60  
  Purchase #4 $36.66   12.685%   $41.3103   $41.31   $41.30   $41.30  
  Purchase #5 $215.99   8.818%   $235.036   $235.04   $235.05   $235.00  
  Purchase #6 $45.27   5.820%   $47.9047   $47.90   $47.90   $47.90  
  Purchase #7 $88.56   13.515%   $100.5289   $100.53   $100.55   $100.50  
  7 purchase totals = $682.63       $753.6923   $753.69   $753.75   $753.50