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	$77.89	6.115%	$82.653	$82.65	$82.65	$82.70
Purchase #2	$60.37	7.452%	$64.8688	$64.87	$64.85	$64.90
Purchase #3	$243.45	9.393%	$266.3173	$266.32	$266.30	$266.30
Purchase #4	$174.40	12.612%	$196.3953	$196.40	$196.40	$196.40
Purchase #5	$242.39	3.799%	$251.5984	$251.60	$251.60	$251.60
Purchase #6	$152.29	8.448%	$165.1555	$165.16	$165.15	$165.20
Purchase #7	$59.52	3.643%	$61.6883	$61.69	$61.70	$61.70
7 purchase totals =	$1,010.31		$1,088.6766	$1,088.69	$1,088.65	$1,088.80