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	$14.94	6.299%	$15.8811	$15.88	$15.90	$15.90
Purchase #2	$233.65	5.784%	$247.1643	$247.16	$247.15	$247.20
Purchase #3	$30.89	5.126%	$32.4734	$32.47	$32.45	$32.50
Purchase #4	$28.27	3.613%	$29.2914	$29.29	$29.30	$29.30
Purchase #5	$141.38	7.817%	$152.4317	$152.43	$152.45	$152.40
Purchase #6	$28.85	11.245%	$32.0942	$32.09	$32.10	$32.10
Purchase #7	$213.46	8.274%	$231.1217	$231.12	$231.10	$231.10
7 purchase totals =	$691.44		$740.4578	$740.44	$740.45	$740.50