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	$179.31	3.503%	$185.5912	$185.59	$185.60	$185.60
Purchase #2	$65.52	7.773%	$70.6129	$70.61	$70.60	$70.60
Purchase #3	$237.63	6.513%	$253.1068	$253.11	$253.10	$253.10
Purchase #4	$116.27	3.204%	$119.9953	$120.00	$120.00	$120.00
Purchase #5	$233.54	4.715%	$244.5514	$244.55	$244.55	$244.60
Purchase #6	$103.72	12.152%	$116.3241	$116.32	$116.30	$116.30
Purchase #7	$233.26	3.520%	$241.4708	$241.47	$241.45	$241.50
7 purchase totals =	$1,169.25		$1,231.6525	$1,231.65	$1,231.60	$1,231.70