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	$161.27	11.819%	$180.3305	$180.33	$180.35	$180.30
Purchase #2	$235.42	5.487%	$248.3375	$248.34	$248.35	$248.30
Purchase #3	$14.94	6.201%	$15.8664	$15.87	$15.85	$15.90
Purchase #4	$43.92	11.180%	$48.8303	$48.83	$48.85	$48.80
Purchase #5	$118.47	4.170%	$123.4102	$123.41	$123.40	$123.40
Purchase #6	$126.31	11.841%	$141.2664	$141.27	$141.25	$141.30
Purchase #7	$33.42	10.702%	$36.9966	$37.00	$37.00	$37.00
7 purchase totals =	$733.75		$795.0379	$795.05	$795.05	$795.00