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 $73.61   3.271%   $76.0178   $76.02   $76.00   $76.00  
  Purchase #2 $173.67   8.162%   $187.8449   $187.84   $187.85   $187.80  
  Purchase #3 $95.76   9.421%   $104.7815   $104.78   $104.80   $104.80  
  Purchase #4 $219.41   9.170%   $239.5299   $239.53   $239.55   $239.50  
  Purchase #5 $173.97   8.265%   $188.3486   $188.35   $188.35   $188.30  
  Purchase #6 $151.48   13.491%   $171.9162   $171.92   $171.90   $171.90  
  Purchase #7 $227.69   12.500%   $256.1513   $256.15   $256.15   $256.20  
  7 purchase totals = $1,115.59       $1,224.5902   $1,224.59   $1,224.60   $1,224.50