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	$64.64	12.793%	$72.9094	$72.91	$72.90	$72.90
Purchase #2	$219.76	6.792%	$234.6861	$234.69	$234.70	$234.70
Purchase #3	$97.55	7.806%	$105.1648	$105.16	$105.15	$105.20
Purchase #4	$159.51	6.603%	$170.0424	$170.04	$170.05	$170.00
Purchase #5	$172.51	12.239%	$193.6235	$193.62	$193.60	$193.60
Purchase #6	$161.53	12.471%	$181.6744	$181.67	$181.65	$181.70
Purchase #7	$139.51	5.644%	$147.3839	$147.38	$147.40	$147.40
7 purchase totals =	$1,015.01		$1,105.4845	$1,105.47	$1,105.45	$1,105.50