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	$116.98	5.544%	$123.4654	$123.47	$123.45	$123.50
Purchase #2	$23.61	10.117%	$25.9986	$26.00	$26.00	$26.00
Purchase #3	$22.32	11.697%	$24.9308	$24.93	$24.95	$24.90
Purchase #4	$245.91	10.219%	$271.0395	$271.04	$271.05	$271.00
Purchase #5	$150.74	10.170%	$166.0703	$166.07	$166.05	$166.10
Purchase #6	$111.76	13.766%	$127.1449	$127.14	$127.15	$127.10
Purchase #7	$165.61	5.589%	$174.8659	$174.87	$174.85	$174.90
7 purchase totals =	$836.93		$913.5154	$913.52	$913.50	$913.50