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 $94.54   4.572%   $98.8624   $98.86   $98.85   $98.90  
  Purchase #2 $169.87   13.213%   $192.3149   $192.31   $192.30   $192.30  
  Purchase #3 $244.52   8.356%   $264.9521   $264.95   $264.95   $265.00  
  Purchase #4 $19.40   8.708%   $21.0894   $21.09   $21.10   $21.10  
  Purchase #5 $192.68   11.347%   $214.5434   $214.54   $214.55   $214.50  
  Purchase #6 $94.46   4.647%   $98.8496   $98.85   $98.85   $98.80  
  Purchase #7 $40.71   8.655%   $44.2335   $44.23   $44.25   $44.20  
  7 purchase totals = $856.18       $934.8453   $934.83   $934.85   $934.80