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	$244.58	4.514%	$255.6203	$255.62	$255.60	$255.60
Purchase #2	$15.67	7.670%	$16.8719	$16.87	$16.85	$16.90
Purchase #3	$100.68	9.297%	$110.0402	$110.04	$110.05	$110.00
Purchase #4	$136.33	13.751%	$155.0767	$155.08	$155.10	$155.10
Purchase #5	$200.31	8.107%	$216.5491	$216.55	$216.55	$216.50
Purchase #6	$111.47	10.482%	$123.1543	$123.15	$123.15	$123.20
Purchase #7	$161.42	7.429%	$173.4119	$173.41	$173.40	$173.40
7 purchase totals =	$970.46		$1,050.7244	$1,050.72	$1,050.70	$1,050.70