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	$209.56	11.487%	$233.6322	$233.63	$233.65	$233.60
Purchase #2	$111.49	7.244%	$119.5663	$119.57	$119.55	$119.60
Purchase #3	$242.74	11.533%	$270.7352	$270.74	$270.75	$270.70
Purchase #4	$229.73	4.175%	$239.3212	$239.32	$239.30	$239.30
Purchase #5	$145.25	13.658%	$165.0882	$165.09	$165.10	$165.10
Purchase #6	$53.72	6.165%	$57.0318	$57.03	$57.05	$57.00
Purchase #7	$117.28	8.726%	$127.5139	$127.51	$127.50	$127.50
7 purchase totals =	$1,109.77		$1,212.8888	$1,212.89	$1,212.90	$1,212.80