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	$208.42	6.188%	$221.317	$221.32	$221.30	$221.30
Purchase #2	$12.56	7.316%	$13.4789	$13.48	$13.50	$13.50
Purchase #3	$104.40	6.746%	$111.4428	$111.44	$111.45	$111.40
Purchase #4	$107.91	3.469%	$111.6534	$111.65	$111.65	$111.70
Purchase #5	$48.36	4.513%	$50.5425	$50.54	$50.55	$50.50
Purchase #6	$229.72	5.861%	$243.1839	$243.18	$243.20	$243.20
Purchase #7	$200.25	6.123%	$212.5113	$212.51	$212.50	$212.50
7 purchase totals =	$911.62		$964.1298	$964.12	$964.15	$964.10