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	$28.89	11.686%	$32.2661	$32.27	$32.25	$32.30
Purchase #2	$150.47	5.233%	$158.3441	$158.34	$158.35	$158.30
Purchase #3	$116.95	6.422%	$124.4605	$124.46	$124.45	$124.50
Purchase #4	$9.46	5.149%	$9.9471	$9.95	$9.95	$9.90
Purchase #5	$173.35	4.712%	$181.5183	$181.52	$181.50	$181.50
Purchase #6	$85.33	5.784%	$90.2655	$90.27	$90.25	$90.30
Purchase #7	$175.84	12.767%	$198.2895	$198.29	$198.30	$198.30
7 purchase totals =	$740.29		$795.0911	$795.10	$795.05	$795.10