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	$32.27	7.374%	$34.6496	$34.65	$34.65	$34.60
Purchase #2	$54.50	8.613%	$59.1941	$59.19	$59.20	$59.20
Purchase #3	$23.29	13.624%	$26.463	$26.46	$26.45	$26.50
Purchase #4	$83.80	6.860%	$89.5487	$89.55	$89.55	$89.50
Purchase #5	$47.84	11.857%	$53.5124	$53.51	$53.50	$53.50
Purchase #6	$54.42	5.264%	$57.2847	$57.28	$57.30	$57.30
Purchase #7	$151.96	8.678%	$165.1471	$165.15	$165.15	$165.10
7 purchase totals =	$448.08		$485.7996	$485.79	$485.80	$485.70