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 $59.26   5.645%   $62.6052   $62.61   $62.60   $62.60  
  Purchase #2 $247.26   13.537%   $280.7316   $280.73   $280.75   $280.70  
  Purchase #3 $34.60   8.788%   $37.6406   $37.64   $37.65   $37.60  
  Purchase #4 $106.84   8.634%   $116.0646   $116.06   $116.05   $116.10  
  Purchase #5 $93.94   10.688%   $103.9803   $103.98   $104.00   $104.00  
  Purchase #6 $162.74   8.593%   $176.7242   $176.72   $176.70   $176.70  
  Purchase #7 $125.65   13.780%   $142.9646   $142.96   $142.95   $143.00  
  7 purchase totals = $830.29       $920.7111   $920.70   $920.70   $920.70