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	$67.78	12.130%	$76.0017	$76.00	$76.00	$76.00
Purchase #2	$21.65	3.662%	$22.4428	$22.44	$22.45	$22.40
Purchase #3	$11.58	9.841%	$12.7196	$12.72	$12.70	$12.70
Purchase #4	$48.40	6.700%	$51.6428	$51.64	$51.65	$51.60
Purchase #5	$21.32	3.817%	$22.1338	$22.13	$22.15	$22.10
Purchase #6	$132.62	6.504%	$141.2456	$141.25	$141.25	$141.20
Purchase #7	$166.32	3.767%	$172.5853	$172.59	$172.60	$172.60
7 purchase totals =	$469.67		$498.7716	$498.77	$498.80	$498.60