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	$41.69	10.857%	$46.2163	$46.22	$46.20	$46.20
Purchase #2	$221.25	3.812%	$229.6841	$229.68	$229.70	$229.70
Purchase #3	$29.67	9.558%	$32.5059	$32.51	$32.50	$32.50
Purchase #4	$194.62	11.239%	$216.4933	$216.49	$216.50	$216.50
Purchase #5	$45.72	13.753%	$52.0079	$52.01	$52.00	$52.00
Purchase #6	$40.37	11.533%	$45.0259	$45.03	$45.05	$45.00
Purchase #7	$105.64	7.278%	$113.3285	$113.33	$113.35	$113.30
7 purchase totals =	$678.96		$735.2619	$735.27	$735.30	$735.20