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 $47.33   3.386%   $48.9326   $48.93   $48.95   $48.90  
  Purchase #2 $10.34   10.860%   $11.4629   $11.46   $11.45   $11.50  
  Purchase #3 $103.49   11.403%   $115.291   $115.29   $115.30   $115.30  
  Purchase #4 $96.36   10.641%   $106.6137   $106.61   $106.60   $106.60  
  Purchase #5 $104.94   10.668%   $116.135   $116.14   $116.15   $116.10  
  Purchase #6 $173.40   3.718%   $179.847   $179.85   $179.85   $179.80  
  Purchase #7 $207.37   3.434%   $214.4911   $214.49   $214.50   $214.50  
  7 purchase totals = $743.23       $792.7733   $792.77   $792.80   $792.70