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	$173.96	3.820%	$180.6053	$180.61	$180.60	$180.60
Purchase #2	$202.27	11.404%	$225.3369	$225.34	$225.35	$225.30
Purchase #3	$233.89	4.419%	$244.2256	$244.23	$244.25	$244.20
Purchase #4	$224.47	13.339%	$254.4121	$254.41	$254.40	$254.40
Purchase #5	$130.40	13.761%	$148.3443	$148.34	$148.35	$148.30
Purchase #6	$133.73	8.795%	$145.4916	$145.49	$145.50	$145.50
Purchase #7	$172.90	3.588%	$179.1037	$179.10	$179.10	$179.10
7 purchase totals =	$1,271.62		$1,377.5195	$1,377.52	$1,377.55	$1,377.40