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	$67.54	6.809%	$72.1388	$72.14	$72.15	$72.10
Purchase #2	$48.29	12.106%	$54.136	$54.14	$54.15	$54.10
Purchase #3	$9.44	11.179%	$10.4953	$10.50	$10.50	$10.50
Purchase #4	$99.46	7.103%	$106.5246	$106.52	$106.50	$106.50
Purchase #5	$26.87	5.678%	$28.3957	$28.40	$28.40	$28.40
Purchase #6	$56.73	3.176%	$58.5317	$58.53	$58.55	$58.50
Purchase #7	$156.77	13.767%	$178.3525	$178.35	$178.35	$178.40
7 purchase totals =	$465.10		$508.5746	$508.58	$508.60	$508.50