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 $84.88   11.571%   $94.7015   $94.70   $94.70   $94.70  
  Purchase #2 $167.72   11.296%   $186.6657   $186.67   $186.65   $186.70  
  Purchase #3 $168.50   5.593%   $177.9242   $177.92   $177.90   $177.90  
  Purchase #4 $71.84   13.756%   $81.7223   $81.72   $81.70   $81.70  
  Purchase #5 $204.81   11.243%   $227.8368   $227.84   $227.85   $227.80  
  Purchase #6 $207.96   12.495%   $233.9446   $233.94   $233.95   $233.90  
  Purchase #7 $116.91   12.635%   $131.6816   $131.68   $131.70   $131.70  
  7 purchase totals = $1,022.62       $1,134.4767   $1,134.47   $1,134.45   $1,134.40