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 $208.64   11.312%   $232.2414   $232.24   $232.25   $232.20  
  Purchase #2 $170.62   10.392%   $188.3508   $188.35   $188.35   $188.40  
  Purchase #3 $178.61   13.637%   $202.967   $202.97   $202.95   $203.00  
  Purchase #4 $161.70   11.744%   $180.69   $180.69   $180.70   $180.70  
  Purchase #5 $83.56   11.192%   $92.912   $92.91   $92.90   $92.90  
  Purchase #6 $117.41   12.576%   $132.1755   $132.18   $132.20   $132.20  
  Purchase #7 $152.55   13.531%   $173.1915   $173.19   $173.20   $173.20  
  7 purchase totals = $1,073.09       $1,202.5282   $1,202.53   $1,202.55   $1,202.60