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	$97.46	8.188%	$105.44	$105.44	$105.45	$105.40
Purchase #2	$123.89	11.309%	$137.9007	$137.90	$137.90	$137.90
Purchase #3	$56.73	8.662%	$61.644	$61.64	$61.65	$61.60
Purchase #4	$98.90	12.326%	$111.0904	$111.09	$111.10	$111.10
Purchase #5	$26.62	11.134%	$29.5839	$29.58	$29.60	$29.60
Purchase #6	$30.94	4.209%	$32.2423	$32.24	$32.25	$32.20
Purchase #7	$9.62	8.676%	$10.4546	$10.45	$10.45	$10.50
7 purchase totals =	$444.16		$488.3559	$488.34	$488.40	$488.30