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	$201.92	13.637%	$229.4558	$229.46	$229.45	$229.50
Purchase #2	$38.34	5.607%	$40.4897	$40.49	$40.50	$40.50
Purchase #3	$26.91	5.539%	$28.4005	$28.40	$28.40	$28.40
Purchase #4	$94.45	10.346%	$104.2218	$104.22	$104.20	$104.20
Purchase #5	$224.92	9.613%	$246.5416	$246.54	$246.55	$246.50
Purchase #6	$243.41	11.485%	$271.3656	$271.37	$271.35	$271.40
Purchase #7	$131.80	10.504%	$145.6443	$145.64	$145.65	$145.60
7 purchase totals =	$961.75		$1,066.1193	$1,066.12	$1,066.10	$1,066.10