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	$209.30	10.517%	$231.3121	$231.31	$231.30	$231.30
Purchase #2	$32.44	6.412%	$34.5201	$34.52	$34.50	$34.50
Purchase #3	$94.63	6.277%	$100.5699	$100.57	$100.55	$100.60
Purchase #4	$122.40	4.467%	$127.8676	$127.87	$127.85	$127.90
Purchase #5	$111.49	13.527%	$126.5713	$126.57	$126.55	$126.60
Purchase #6	$234.77	5.198%	$246.9733	$246.97	$246.95	$247.00
Purchase #7	$171.39	13.846%	$195.1207	$195.12	$195.10	$195.10
7 purchase totals =	$976.42		$1,062.9350	$1,062.93	$1,062.80	$1,063.00