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	$207.38	3.348%	$214.3231	$214.32	$214.30	$214.30
Purchase #2	$100.71	12.369%	$113.1668	$113.17	$113.15	$113.20
Purchase #3	$111.98	13.388%	$126.9719	$126.97	$126.95	$127.00
Purchase #4	$74.61	5.594%	$78.7837	$78.78	$78.80	$78.80
Purchase #5	$232.89	9.290%	$254.5255	$254.53	$254.55	$254.50
Purchase #6	$123.80	13.320%	$140.2902	$140.29	$140.30	$140.30
Purchase #7	$165.61	13.842%	$188.5337	$188.53	$188.55	$188.50
7 purchase totals =	$1,016.98		$1,116.5949	$1,116.59	$1,116.60	$1,116.60