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	$62.82	7.395%	$67.4655	$67.47	$67.45	$67.50
Purchase #2	$132.70	5.594%	$140.1232	$140.12	$140.10	$140.10
Purchase #3	$99.37	11.858%	$111.1533	$111.15	$111.15	$111.20
Purchase #4	$35.32	6.332%	$37.5565	$37.56	$37.55	$37.60
Purchase #5	$68.27	4.581%	$71.3974	$71.40	$71.40	$71.40
Purchase #6	$170.43	4.275%	$177.7159	$177.72	$177.70	$177.70
Purchase #7	$220.26	11.112%	$244.7353	$244.74	$244.75	$244.70
7 purchase totals =	$789.17		$850.1471	$850.16	$850.10	$850.20