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 $60.94   3.298%   $62.9498   $62.95   $62.95   $62.90  
  Purchase #2 $32.76   5.827%   $34.6689   $34.67   $34.65   $34.70  
  Purchase #3 $114.77   7.226%   $123.0633   $123.06   $123.05   $123.10  
  Purchase #4 $38.81   3.381%   $40.1222   $40.12   $40.10   $40.10  
  Purchase #5 $204.35   13.407%   $231.7472   $231.75   $231.75   $231.70  
  Purchase #6 $242.52   6.390%   $258.017   $258.02   $258.00   $258.00  
  Purchase #7 $197.67   6.608%   $210.732   $210.73   $210.75   $210.70  
  7 purchase totals = $891.82       $961.3004   $961.30   $961.25   $961.20