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 $158.28   10.518%   $174.9279   $174.93   $174.95   $174.90  
  Purchase #2 $69.72   8.249%   $75.4712   $75.47   $75.45   $75.50  
  Purchase #3 $226.88   4.712%   $237.5706   $237.57   $237.55   $237.60  
  Purchase #4 $144.75   6.777%   $154.5597   $154.56   $154.55   $154.60  
  Purchase #5 $32.68   11.843%   $36.5503   $36.55   $36.55   $36.60  
  Purchase #6 $219.42   5.695%   $231.916   $231.92   $231.90   $231.90  
  Purchase #7 $13.38   4.507%   $13.983   $13.98   $14.00   $14.00  
  7 purchase totals = $865.11       $924.9787   $924.98   $924.95   $925.10