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	$117.40	4.466%	$122.6431	$122.64	$122.65	$122.60
Purchase #2	$63.26	3.320%	$65.3602	$65.36	$65.35	$65.40
Purchase #3	$173.96	6.607%	$185.4535	$185.45	$185.45	$185.50
Purchase #4	$139.26	6.866%	$148.8216	$148.82	$148.80	$148.80
Purchase #5	$153.47	12.120%	$172.0706	$172.07	$172.05	$172.10
Purchase #6	$160.61	6.546%	$171.1235	$171.12	$171.10	$171.10
Purchase #7	$126.59	8.417%	$137.2451	$137.25	$137.25	$137.20
7 purchase totals =	$934.55		$1,002.7176	$1,002.71	$1,002.65	$1,002.70