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	$136.51	11.266%	$151.8892	$151.89	$151.90	$151.90
Purchase #2	$20.28	5.117%	$21.3177	$21.32	$21.30	$21.30
Purchase #3	$11.61	10.435%	$12.8215	$12.82	$12.80	$12.80
Purchase #4	$16.95	8.833%	$18.4472	$18.45	$18.45	$18.40
Purchase #5	$116.72	10.577%	$129.0655	$129.07	$129.05	$129.10
Purchase #6	$100.28	5.267%	$105.5617	$105.56	$105.55	$105.60
Purchase #7	$232.49	4.795%	$243.6379	$243.64	$243.65	$243.60
7 purchase totals =	$634.84		$682.7407	$682.75	$682.70	$682.70