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 $202.63   5.853%   $214.4899   $214.49   $214.50   $214.50  
  Purchase #2 $170.55   9.161%   $186.1741   $186.17   $186.15   $186.20  
  Purchase #3 $11.26   6.123%   $11.9494   $11.95   $11.95   $11.90  
  Purchase #4 $118.47   4.105%   $123.3332   $123.33   $123.35   $123.30  
  Purchase #5 $163.91   3.184%   $169.1289   $169.13   $169.15   $169.10  
  Purchase #6 $48.28   9.634%   $52.9313   $52.93   $52.95   $52.90  
  Purchase #7 $104.50   11.577%   $116.598   $116.60   $116.60   $116.60  
  7 purchase totals = $819.60       $874.6048   $874.60   $874.65   $874.50