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	$64.82	10.569%	$71.6708	$71.67	$71.65	$71.70
Purchase #2	$124.35	13.631%	$141.3001	$141.30	$141.30	$141.30
Purchase #3	$231.42	9.647%	$253.7451	$253.75	$253.75	$253.70
Purchase #4	$28.44	10.809%	$31.5141	$31.51	$31.50	$31.50
Purchase #5	$48.29	4.203%	$50.3196	$50.32	$50.30	$50.30
Purchase #6	$154.40	4.600%	$161.5024	$161.50	$161.50	$161.50
Purchase #7	$167.78	11.178%	$186.5344	$186.53	$186.55	$186.50
7 purchase totals =	$819.50		$896.5865	$896.58	$896.55	$896.50