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 $87.52   8.264%   $94.7527   $94.75   $94.75   $94.80  
  Purchase #2 $35.56   8.569%   $38.6071   $38.61   $38.60   $38.60  
  Purchase #3 $118.78   12.713%   $133.8805   $133.88   $133.90   $133.90  
  Purchase #4 $104.52   3.357%   $108.0287   $108.03   $108.05   $108.00  
  Purchase #5 $172.81   8.538%   $187.5645   $187.56   $187.55   $187.60  
  Purchase #6 $110.75   6.559%   $118.0141   $118.01   $118.00   $118.00  
  Purchase #7 $67.75   8.216%   $73.3163   $73.32   $73.30   $73.30  
  7 purchase totals = $697.69       $754.1639   $754.16   $754.15   $754.20