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	$153.31	4.603%	$160.3669	$160.37	$160.35	$160.40
Purchase #2	$207.62	12.345%	$233.2507	$233.25	$233.25	$233.30
Purchase #3	$69.27	4.584%	$72.4453	$72.45	$72.45	$72.40
Purchase #4	$152.96	10.112%	$168.4273	$168.43	$168.45	$168.40
Purchase #5	$241.52	4.151%	$251.5455	$251.55	$251.55	$251.50
Purchase #6	$24.56	8.357%	$26.6125	$26.61	$26.60	$26.60
Purchase #7	$99.58	10.681%	$110.2161	$110.22	$110.20	$110.20
7 purchase totals =	$948.82		$1,022.8643	$1,022.88	$1,022.85	$1,022.80