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	$41.87	13.328%	$47.4504	$47.45	$47.45	$47.50
Purchase #2	$122.34	5.506%	$129.076	$129.08	$129.10	$129.10
Purchase #3	$33.56	13.532%	$38.1013	$38.10	$38.10	$38.10
Purchase #4	$91.39	4.222%	$95.2485	$95.25	$95.25	$95.20
Purchase #5	$214.35	13.445%	$243.1694	$243.17	$243.15	$243.20
Purchase #6	$40.49	13.184%	$45.8282	$45.83	$45.85	$45.80
Purchase #7	$95.40	6.503%	$101.6039	$101.60	$101.60	$101.60
7 purchase totals =	$639.40		$700.4777	$700.48	$700.50	$700.50