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	$248.94	3.183%	$256.8638	$256.86	$256.85	$256.90
Purchase #2	$20.82	3.460%	$21.5404	$21.54	$21.55	$21.50
Purchase #3	$19.93	11.848%	$22.2913	$22.29	$22.30	$22.30
Purchase #4	$32.62	4.514%	$34.0925	$34.09	$34.10	$34.10
Purchase #5	$77.75	4.547%	$81.2853	$81.29	$81.30	$81.30
Purchase #6	$32.39	4.271%	$33.7734	$33.77	$33.75	$33.80
Purchase #7	$165.86	6.495%	$176.6326	$176.63	$176.65	$176.60
7 purchase totals =	$598.31		$626.4793	$626.47	$626.50	$626.50