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 $162.73   8.434%   $176.4546   $176.45   $176.45   $176.50  
  Purchase #2 $96.98   5.128%   $101.9531   $101.95   $101.95   $102.00  
  Purchase #3 $60.57   9.766%   $66.4853   $66.49   $66.50   $66.50  
  Purchase #4 $160.71   11.593%   $179.3411   $179.34   $179.35   $179.30  
  Purchase #5 $196.86   8.291%   $213.1817   $213.18   $213.20   $213.20  
  Purchase #6 $136.61   9.600%   $149.7246   $149.72   $149.70   $149.70  
  Purchase #7 $68.59   13.524%   $77.8661   $77.87   $77.85   $77.90  
  7 purchase totals = $883.05       $965.0065   $965.00   $965.00   $965.10