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	$96.29	5.171%	$101.2692	$101.27	$101.25	$101.30
Purchase #2	$227.27	12.228%	$255.0606	$255.06	$255.05	$255.10
Purchase #3	$177.91	4.253%	$185.4765	$185.48	$185.50	$185.50
Purchase #4	$43.86	9.452%	$48.0056	$48.01	$48.00	$48.00
Purchase #5	$10.75	13.238%	$12.1731	$12.17	$12.15	$12.20
Purchase #6	$165.95	4.709%	$173.7646	$173.76	$173.75	$173.80
Purchase #7	$227.58	3.727%	$236.0619	$236.06	$236.05	$236.10
7 purchase totals =	$949.61		$1,011.8115	$1,011.81	$1,011.75	$1,012.00