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	$127.89	3.450%	$132.3022	$132.30	$132.30	$132.30
Purchase #2	$225.52	12.402%	$253.489	$253.49	$253.50	$253.50
Purchase #3	$178.89	12.434%	$201.1332	$201.13	$201.15	$201.10
Purchase #4	$48.76	11.256%	$54.2484	$54.25	$54.25	$54.20
Purchase #5	$158.37	11.428%	$176.4685	$176.47	$176.45	$176.50
Purchase #6	$180.96	5.442%	$190.8078	$190.81	$190.80	$190.80
Purchase #7	$127.55	13.122%	$144.2871	$144.29	$144.30	$144.30
7 purchase totals =	$1,047.94		$1,152.7362	$1,152.74	$1,152.75	$1,152.70