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 $62.90   10.431%   $69.4611   $69.46   $69.45   $69.50  
  Purchase #2 $62.79   12.221%   $70.4636   $70.46   $70.45   $70.50  
  Purchase #3 $86.83   9.593%   $95.1596   $95.16   $95.15   $95.20  
  Purchase #4 $34.41   5.548%   $36.3191   $36.32   $36.30   $36.30  
  Purchase #5 $156.63   4.778%   $164.1138   $164.11   $164.10   $164.10  
  Purchase #6 $139.47   7.185%   $149.4909   $149.49   $149.50   $149.50  
  Purchase #7 $164.70   7.561%   $177.153   $177.15   $177.15   $177.20  
  7 purchase totals = $707.73       $762.1611   $762.15   $762.10   $762.30