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 $58.68   5.807%   $62.0875   $62.09   $62.10   $62.10  
  Purchase #2 $53.95   8.736%   $58.6631   $58.66   $58.65   $58.70  
  Purchase #3 $161.95   8.599%   $175.8761   $175.88   $175.90   $175.90  
  Purchase #4 $178.83   11.474%   $199.349   $199.35   $199.35   $199.30  
  Purchase #5 $86.49   11.376%   $96.3291   $96.33   $96.35   $96.30  
  Purchase #6 $89.44   5.766%   $94.5971   $94.60   $94.60   $94.60  
  Purchase #7 $40.91   11.663%   $45.6813   $45.68   $45.70   $45.70  
  7 purchase totals = $670.25       $732.5832   $732.59   $732.65   $732.60