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 $176.82   11.674%   $197.462   $197.46   $197.45   $197.50  
  Purchase #2 $154.92   12.734%   $174.6475   $174.65   $174.65   $174.60  
  Purchase #3 $99.95   3.820%   $103.7681   $103.77   $103.75   $103.80  
  Purchase #4 $144.96   12.293%   $162.7799   $162.78   $162.80   $162.80  
  Purchase #5 $148.81   9.739%   $163.3026   $163.30   $163.30   $163.30  
  Purchase #6 $102.95   5.102%   $108.2025   $108.20   $108.20   $108.20  
  Purchase #7 $87.43   11.601%   $97.5728   $97.57   $97.55   $97.60  
  7 purchase totals = $915.84       $1,007.7354   $1,007.73   $1,007.70   $1,007.80