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	$209.37	12.477%	$235.4931	$235.49	$235.50	$235.50
Purchase #2	$118.61	6.445%	$126.2544	$126.25	$126.25	$126.30
Purchase #3	$108.41	4.344%	$113.1193	$113.12	$113.10	$113.10
Purchase #4	$197.96	10.411%	$218.5696	$218.57	$218.55	$218.60
Purchase #5	$81.56	10.527%	$90.1458	$90.15	$90.15	$90.10
Purchase #6	$173.29	4.695%	$181.426	$181.43	$181.45	$181.40
Purchase #7	$94.56	11.465%	$105.4013	$105.40	$105.40	$105.40
7 purchase totals =	$983.76		$1,070.4095	$1,070.41	$1,070.40	$1,070.40