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	$116.56	12.201%	$130.7815	$130.78	$130.80	$130.80
Purchase #2	$247.46	5.249%	$260.4492	$260.45	$260.45	$260.40
Purchase #3	$87.54	13.823%	$99.6407	$99.64	$99.65	$99.60
Purchase #4	$100.26	11.683%	$111.9734	$111.97	$111.95	$112.00
Purchase #5	$129.76	7.452%	$139.4297	$139.43	$139.45	$139.40
Purchase #6	$197.59	5.428%	$208.3152	$208.32	$208.30	$208.30
Purchase #7	$181.77	5.443%	$191.6637	$191.66	$191.65	$191.70
7 purchase totals =	$1,060.94		$1,142.2534	$1,142.25	$1,142.25	$1,142.20