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	$53.55	11.422%	$59.6665	$59.67	$59.65	$59.70
Purchase #2	$124.99	5.137%	$131.4107	$131.41	$131.40	$131.40
Purchase #3	$11.27	5.435%	$11.8825	$11.88	$11.90	$11.90
Purchase #4	$183.34	4.536%	$191.6563	$191.66	$191.65	$191.70
Purchase #5	$133.83	3.615%	$138.668	$138.67	$138.65	$138.70
Purchase #6	$33.54	5.225%	$35.2925	$35.29	$35.30	$35.30
Purchase #7	$83.59	11.592%	$93.2798	$93.28	$93.30	$93.30
7 purchase totals =	$624.11		$661.8563	$661.86	$661.85	$662.00