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	$43.25	4.469%	$45.1828	$45.18	$45.20	$45.20
Purchase #2	$157.84	13.636%	$179.3631	$179.36	$179.35	$179.40
Purchase #3	$47.43	6.789%	$50.65	$50.65	$50.65	$50.70
Purchase #4	$11.70	10.505%	$12.9291	$12.93	$12.95	$12.90
Purchase #5	$177.40	10.579%	$196.1671	$196.17	$196.15	$196.20
Purchase #6	$126.72	9.175%	$138.3466	$138.35	$138.35	$138.30
Purchase #7	$72.43	6.822%	$77.3712	$77.37	$77.35	$77.40
7 purchase totals =	$636.77		$700.0099	$700.01	$700.00	$700.10