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	$52.66	12.106%	$59.035	$59.04	$59.05	$59.00
Purchase #2	$227.68	10.403%	$251.3656	$251.37	$251.35	$251.40
Purchase #3	$186.97	4.556%	$195.4884	$195.49	$195.50	$195.50
Purchase #4	$127.74	9.510%	$139.8881	$139.89	$139.90	$139.90
Purchase #5	$127.52	11.201%	$141.8035	$141.80	$141.80	$141.80
Purchase #6	$216.92	11.369%	$241.5816	$241.58	$241.60	$241.60
Purchase #7	$11.30	10.242%	$12.4573	$12.46	$12.45	$12.50
7 purchase totals =	$950.79		$1,041.6195	$1,041.63	$1,041.65	$1,041.70