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	$189.52	12.243%	$212.7229	$212.72	$212.70	$212.70
Purchase #2	$89.62	4.153%	$93.3419	$93.34	$93.35	$93.30
Purchase #3	$56.30	6.242%	$59.8142	$59.81	$59.80	$59.80
Purchase #4	$176.51	6.481%	$187.9496	$187.95	$187.95	$187.90
Purchase #5	$138.71	9.583%	$152.0026	$152.00	$152.00	$152.00
Purchase #6	$200.92	4.767%	$210.4979	$210.50	$210.50	$210.50
Purchase #7	$235.27	11.471%	$262.2578	$262.26	$262.25	$262.30
7 purchase totals =	$1,086.85		$1,178.5869	$1,178.58	$1,178.55	$1,178.50