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	$43.82	3.560%	$45.38	$45.38	$45.40	$45.40
Purchase #2	$57.59	7.813%	$62.0895	$62.09	$62.10	$62.10
Purchase #3	$52.39	3.150%	$54.0403	$54.04	$54.05	$54.00
Purchase #4	$34.61	10.792%	$38.3451	$38.35	$38.35	$38.30
Purchase #5	$174.86	5.388%	$184.2815	$184.28	$184.30	$184.30
Purchase #6	$79.67	4.360%	$83.1436	$83.14	$83.15	$83.10
Purchase #7	$151.76	3.574%	$157.1839	$157.18	$157.20	$157.20
7 purchase totals =	$594.70		$624.4639	$624.46	$624.55	$624.40