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 $70.75   8.162%   $76.5246   $76.52   $76.50   $76.50  
  Purchase #2 $198.26   9.362%   $216.8211   $216.82   $216.80   $216.80  
  Purchase #3 $20.61   6.849%   $22.0216   $22.02   $22.00   $22.00  
  Purchase #4 $53.46   8.137%   $57.81   $57.81   $57.80   $57.80  
  Purchase #5 $166.30   13.420%   $188.6175   $188.62   $188.60   $188.60  
  Purchase #6 $37.90   8.809%   $41.2386   $41.24   $41.25   $41.20  
  Purchase #7 $176.81   10.117%   $194.6979   $194.70   $194.70   $194.70  
  7 purchase totals = $724.09       $797.7313   $797.73   $797.65   $797.60