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 $182.90   7.770%   $197.1113   $197.11   $197.10   $197.10  
  Purchase #2 $152.85   3.163%   $157.6846   $157.68   $157.70   $157.70  
  Purchase #3 $68.95   8.663%   $74.9231   $74.92   $74.90   $74.90  
  Purchase #4 $112.85   9.358%   $123.4105   $123.41   $123.40   $123.40  
  Purchase #5 $68.81   12.411%   $77.35   $77.35   $77.35   $77.40  
  Purchase #6 $234.49   8.454%   $254.3138   $254.31   $254.30   $254.30  
  Purchase #7 $10.86   13.627%   $12.3399   $12.34   $12.35   $12.30  
  7 purchase totals = $831.71       $897.1332   $897.12   $897.10   $897.10