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	$55.93	9.628%	$61.3149	$61.31	$61.30	$61.30
Purchase #2	$125.83	10.103%	$138.5426	$138.54	$138.55	$138.50
Purchase #3	$57.84	4.406%	$60.3884	$60.39	$60.40	$60.40
Purchase #4	$162.68	10.130%	$179.1595	$179.16	$179.15	$179.20
Purchase #5	$250.44	13.203%	$283.5056	$283.51	$283.50	$283.50
Purchase #6	$204.55	13.373%	$231.9045	$231.90	$231.90	$231.90
Purchase #7	$60.88	10.834%	$67.4757	$67.48	$67.50	$67.50
7 purchase totals =	$918.15		$1,022.2912	$1,022.29	$1,022.30	$1,022.30