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	$157.67	5.385%	$166.1605	$166.16	$166.15	$166.20
Purchase #2	$72.50	5.559%	$76.5303	$76.53	$76.55	$76.50
Purchase #3	$107.73	3.716%	$111.7332	$111.73	$111.75	$111.70
Purchase #4	$39.77	12.541%	$44.7576	$44.76	$44.75	$44.80
Purchase #5	$43.89	3.497%	$45.4248	$45.42	$45.40	$45.40
Purchase #6	$59.44	4.383%	$62.0453	$62.05	$62.05	$62.00
Purchase #7	$64.46	3.800%	$66.9095	$66.91	$66.90	$66.90
7 purchase totals =	$545.46		$573.5612	$573.56	$573.55	$573.50