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 $195.82   12.193%   $219.6963   $219.70   $219.70   $219.70  
  Purchase #2 $47.69   8.308%   $51.6521   $51.65   $51.65   $51.70  
  Purchase #3 $217.83   9.568%   $238.672   $238.67   $238.65   $238.70  
  Purchase #4 $192.38   13.858%   $219.04   $219.04   $219.05   $219.00  
  Purchase #5 $90.71   4.561%   $94.8473   $94.85   $94.85   $94.80  
  Purchase #6 $26.62   8.519%   $28.8878   $28.89   $28.90   $28.90  
  Purchase #7 $22.48   6.705%   $23.9873   $23.99   $24.00   $24.00  
  7 purchase totals = $793.53       $876.7828   $876.79   $876.80   $876.80