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 $54.97   13.394%   $62.3327   $62.33   $62.35   $62.30  
  Purchase #2 $71.88   7.344%   $77.1589   $77.16   $77.15   $77.20  
  Purchase #3 $177.31   5.131%   $186.4078   $186.41   $186.40   $186.40  
  Purchase #4 $52.90   9.346%   $57.844   $57.84   $57.85   $57.80  
  Purchase #5 $65.25   6.163%   $69.2714   $69.27   $69.25   $69.30  
  Purchase #6 $108.94   6.807%   $116.3555   $116.36   $116.35   $116.40  
  Purchase #7 $171.85   12.544%   $193.4069   $193.41   $193.40   $193.40  
  7 purchase totals = $703.10       $762.7772   $762.78   $762.75   $762.80