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	$30.79	7.262%	$33.026	$33.03	$33.05	$33.00
Purchase #2	$48.53	3.791%	$50.3698	$50.37	$50.35	$50.40
Purchase #3	$128.43	12.211%	$144.1126	$144.11	$144.10	$144.10
Purchase #4	$25.39	6.383%	$27.0106	$27.01	$27.00	$27.00
Purchase #5	$66.68	9.425%	$72.9646	$72.96	$72.95	$73.00
Purchase #6	$86.76	7.307%	$93.0996	$93.10	$93.10	$93.10
Purchase #7	$196.37	13.530%	$222.9389	$222.94	$222.95	$222.90
7 purchase totals =	$582.95		$643.5221	$643.52	$643.50	$643.50