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	$215.33	12.419%	$242.0718	$242.07	$242.05	$242.10
Purchase #2	$48.64	13.733%	$55.3197	$55.32	$55.30	$55.30
Purchase #3	$59.83	13.431%	$67.8658	$67.87	$67.85	$67.90
Purchase #4	$165.73	3.280%	$171.1659	$171.17	$171.15	$171.20
Purchase #5	$165.61	4.122%	$172.4364	$172.44	$172.45	$172.40
Purchase #6	$90.60	11.207%	$100.7535	$100.75	$100.75	$100.80
Purchase #7	$202.58	3.634%	$209.9418	$209.94	$209.95	$209.90
7 purchase totals =	$948.32		$1,019.5549	$1,019.56	$1,019.50	$1,019.60