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 $59.84   5.488%   $63.124   $63.12   $63.10   $63.10  
  Purchase #2 $157.74   11.789%   $176.336   $176.34   $176.35   $176.30  
  Purchase #3 $216.31   11.812%   $241.8605   $241.86   $241.85   $241.90  
  Purchase #4 $201.32   13.763%   $229.0277   $229.03   $229.05   $229.00  
  Purchase #5 $236.40   8.276%   $255.9645   $255.96   $255.95   $256.00  
  Purchase #6 $132.81   12.388%   $149.2625   $149.26   $149.25   $149.30  
  Purchase #7 $107.97   9.483%   $118.2088   $118.21   $118.20   $118.20  
  7 purchase totals = $1,112.39       $1,233.7840   $1,233.78   $1,233.75   $1,233.80