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 $174.45   12.760%   $196.7098   $196.71   $196.70   $196.70  
  Purchase #2 $43.93   6.521%   $46.7947   $46.79   $46.80   $46.80  
  Purchase #3 $50.63   5.658%   $53.4946   $53.49   $53.50   $53.50  
  Purchase #4 $57.89   9.173%   $63.2002   $63.20   $63.20   $63.20  
  Purchase #5 $77.96   13.447%   $88.4433   $88.44   $88.45   $88.40  
  Purchase #6 $221.64   6.364%   $235.7452   $235.75   $235.75   $235.70  
  Purchase #7 $242.54   10.407%   $267.7811   $267.78   $267.80   $267.80  
  7 purchase totals = $869.04       $952.1689   $952.16   $952.20   $952.10