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	$33.56	10.354%	$37.0348	$37.03	$37.05	$37.00
Purchase #2	$54.25	9.196%	$59.2388	$59.24	$59.25	$59.20
Purchase #3	$248.70	13.834%	$283.1052	$283.11	$283.10	$283.10
Purchase #4	$56.44	11.279%	$62.8059	$62.81	$62.80	$62.80
Purchase #5	$76.47	3.625%	$79.242	$79.24	$79.25	$79.20
Purchase #6	$211.43	8.735%	$229.8984	$229.90	$229.90	$229.90
Purchase #7	$106.73	4.231%	$111.2457	$111.25	$111.25	$111.20
7 purchase totals =	$787.58		$862.5708	$862.58	$862.60	$862.40