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	$147.59	9.467%	$161.5623	$161.56	$161.55	$161.60
Purchase #2	$132.43	5.447%	$139.6435	$139.64	$139.65	$139.60
Purchase #3	$232.46	9.146%	$253.7208	$253.72	$253.70	$253.70
Purchase #4	$112.90	10.205%	$124.4214	$124.42	$124.40	$124.40
Purchase #5	$223.46	8.548%	$242.5614	$242.56	$242.55	$242.60
Purchase #6	$67.32	8.183%	$72.8288	$72.83	$72.85	$72.80
Purchase #7	$113.41	4.300%	$118.2866	$118.29	$118.30	$118.30
7 purchase totals =	$1,029.57		$1,113.0248	$1,113.02	$1,113.00	$1,113.00