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	$71.82	8.748%	$78.1028	$78.10	$78.10	$78.10
Purchase #2	$46.51	8.827%	$50.6154	$50.62	$50.60	$50.60
Purchase #3	$35.52	13.609%	$40.3539	$40.35	$40.35	$40.40
Purchase #4	$7.83	11.669%	$8.7437	$8.74	$8.75	$8.70
Purchase #5	$197.38	11.572%	$220.2208	$220.22	$220.20	$220.20
Purchase #6	$160.78	6.806%	$171.7227	$171.72	$171.70	$171.70
Purchase #7	$77.48	6.613%	$82.6038	$82.60	$82.60	$82.60
7 purchase totals =	$597.32		$652.3631	$652.35	$652.30	$652.30