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	$151.57	4.480%	$158.3603	$158.36	$158.35	$158.40
Purchase #2	$12.77	8.253%	$13.8239	$13.82	$13.80	$13.80
Purchase #3	$175.64	7.274%	$188.4161	$188.42	$188.40	$188.40
Purchase #4	$216.44	7.118%	$231.8462	$231.85	$231.85	$231.80
Purchase #5	$172.91	4.679%	$181.0005	$181.00	$181.00	$181.00
Purchase #6	$72.53	13.146%	$82.0648	$82.06	$82.05	$82.10
Purchase #7	$149.80	7.150%	$160.5107	$160.51	$160.50	$160.50
7 purchase totals =	$951.66		$1,016.0225	$1,016.02	$1,015.95	$1,016.00