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 $114.83   7.596%   $123.5525   $123.55   $123.55   $123.60  
  Purchase #2 $125.84   7.798%   $135.653   $135.65   $135.65   $135.70  
  Purchase #3 $68.84   9.215%   $75.1836   $75.18   $75.20   $75.20  
  Purchase #4 $146.61   3.491%   $151.7282   $151.73   $151.75   $151.70  
  Purchase #5 $29.42   6.125%   $31.222   $31.22   $31.20   $31.20  
  Purchase #6 $87.76   6.709%   $93.6478   $93.65   $93.65   $93.60  
  Purchase #7 $187.79   6.569%   $200.1259   $200.13   $200.15   $200.10  
  7 purchase totals = $761.09       $811.1130   $811.11   $811.15   $811.10