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 $44.36   5.808%   $46.9364   $46.94   $46.95   $46.90  
  Purchase #2 $138.71   12.234%   $155.6798   $155.68   $155.70   $155.70  
  Purchase #3 $178.62   3.562%   $184.9824   $184.98   $185.00   $185.00  
  Purchase #4 $88.41   8.587%   $96.0018   $96.00   $96.00   $96.00  
  Purchase #5 $155.35   6.224%   $165.019   $165.02   $165.00   $165.00  
  Purchase #6 $79.93   3.567%   $82.7811   $82.78   $82.80   $82.80  
  Purchase #7 $218.46   8.631%   $237.3153   $237.32   $237.30   $237.30  
  7 purchase totals = $903.84       $968.7158   $968.72   $968.75   $968.70