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	$197.91	12.713%	$223.0703	$223.07	$223.05	$223.10
Purchase #2	$165.32	4.429%	$172.642	$172.64	$172.65	$172.60
Purchase #3	$162.50	3.104%	$167.544	$167.54	$167.55	$167.50
Purchase #4	$78.30	11.584%	$87.3703	$87.37	$87.35	$87.40
Purchase #5	$17.69	4.174%	$18.4284	$18.43	$18.45	$18.40
Purchase #6	$68.30	4.314%	$71.2465	$71.25	$71.25	$71.20
Purchase #7	$102.68	13.271%	$116.3067	$116.31	$116.30	$116.30
7 purchase totals =	$792.70		$856.6082	$856.61	$856.60	$856.50