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	$33.28	6.820%	$35.5497	$35.55	$35.55	$35.50
Purchase #2	$53.64	11.149%	$59.6203	$59.62	$59.60	$59.60
Purchase #3	$210.41	9.447%	$230.2874	$230.29	$230.30	$230.30
Purchase #4	$91.79	8.539%	$99.6279	$99.63	$99.65	$99.60
Purchase #5	$228.66	7.603%	$246.045	$246.05	$246.05	$246.00
Purchase #6	$156.89	12.637%	$176.7162	$176.72	$176.70	$176.70
Purchase #7	$226.44	13.251%	$256.4456	$256.45	$256.45	$256.40
7 purchase totals =	$1,001.11		$1,104.2921	$1,104.31	$1,104.30	$1,104.10