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	$199.81	11.552%	$222.8921	$222.89	$222.90	$222.90
Purchase #2	$97.59	13.153%	$110.426	$110.43	$110.45	$110.40
Purchase #3	$52.65	4.772%	$55.1625	$55.16	$55.15	$55.20
Purchase #4	$88.96	6.594%	$94.826	$94.83	$94.85	$94.80
Purchase #5	$48.28	9.411%	$52.8236	$52.82	$52.80	$52.80
Purchase #6	$9.97	7.488%	$10.7166	$10.72	$10.70	$10.70
Purchase #7	$167.89	9.272%	$183.4568	$183.46	$183.45	$183.50
7 purchase totals =	$665.15		$730.3036	$730.31	$730.30	$730.30