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 $62.73   8.441%   $68.025   $68.03   $68.05   $68.00  
  Purchase #2 $174.39   9.651%   $191.2204   $191.22   $191.20   $191.20  
  Purchase #3 $62.73   11.862%   $70.171   $70.17   $70.15   $70.20  
  Purchase #4 $205.57   3.826%   $213.4351   $213.44   $213.45   $213.40  
  Purchase #5 $232.98   4.239%   $242.856   $242.86   $242.85   $242.90  
  Purchase #6 $79.61   11.448%   $88.7238   $88.72   $88.70   $88.70  
  Purchase #7 $79.64   9.695%   $87.3611   $87.36   $87.35   $87.40  
  7 purchase totals = $897.65       $961.7924   $961.80   $961.75   $961.80