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	$10.54	5.436%	$11.113	$11.11	$11.10	$11.10
Purchase #2	$72.25	5.241%	$76.0366	$76.04	$76.05	$76.00
Purchase #3	$124.90	4.588%	$130.6304	$130.63	$130.65	$130.60
Purchase #4	$219.83	4.538%	$229.8059	$229.81	$229.80	$229.80
Purchase #5	$81.57	10.738%	$90.329	$90.33	$90.35	$90.30
Purchase #6	$95.66	10.178%	$105.3963	$105.40	$105.40	$105.40
Purchase #7	$123.60	11.235%	$137.4865	$137.49	$137.50	$137.50
7 purchase totals =	$728.35		$780.7977	$780.81	$780.85	$780.70