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 $43.98   5.832%   $46.5449   $46.54   $46.55   $46.50  
  Purchase #2 $33.60   8.486%   $36.4513   $36.45   $36.45   $36.50  
  Purchase #3 $60.71   10.789%   $67.26   $67.26   $67.25   $67.30  
  Purchase #4 $212.69   3.521%   $220.1788   $220.18   $220.20   $220.20  
  Purchase #5 $60.43   12.552%   $68.0152   $68.02   $68.00   $68.00  
  Purchase #6 $199.53   11.312%   $222.1008   $222.10   $222.10   $222.10  
  Purchase #7 $87.79   9.200%   $95.8667   $95.87   $95.85   $95.90  
  7 purchase totals = $698.73       $756.4177   $756.42   $756.40   $756.50