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	$43.47	11.461%	$48.4521	$48.45	$48.45	$48.50
Purchase #2	$231.37	4.761%	$242.3855	$242.39	$242.40	$242.40
Purchase #3	$94.40	6.370%	$100.4133	$100.41	$100.40	$100.40
Purchase #4	$8.95	4.755%	$9.3756	$9.38	$9.40	$9.40
Purchase #5	$132.42	13.862%	$150.7761	$150.78	$150.80	$150.80
Purchase #6	$123.68	4.663%	$129.4472	$129.45	$129.45	$129.40
Purchase #7	$66.49	8.610%	$72.2148	$72.21	$72.20	$72.20
7 purchase totals =	$700.78		$753.0646	$753.07	$753.10	$753.10