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	$38.48	6.430%	$40.9543	$40.95	$40.95	$41.00
Purchase #2	$232.44	8.238%	$251.5884	$251.59	$251.60	$251.60
Purchase #3	$132.49	10.859%	$146.8771	$146.88	$146.90	$146.90
Purchase #4	$180.69	10.721%	$200.0618	$200.06	$200.05	$200.10
Purchase #5	$243.86	11.608%	$272.1673	$272.17	$272.15	$272.20
Purchase #6	$241.69	3.793%	$250.8573	$250.86	$250.85	$250.90
Purchase #7	$111.93	4.145%	$116.5695	$116.57	$116.55	$116.60
7 purchase totals =	$1,181.58		$1,279.0757	$1,279.08	$1,279.05	$1,279.30