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	$191.34	10.731%	$211.8727	$211.87	$211.85	$211.90
Purchase #2	$97.57	12.243%	$109.5155	$109.52	$109.50	$109.50
Purchase #3	$170.59	3.284%	$176.1922	$176.19	$176.20	$176.20
Purchase #4	$216.86	7.829%	$233.838	$233.84	$233.85	$233.80
Purchase #5	$43.31	3.839%	$44.9727	$44.97	$44.95	$45.00
Purchase #6	$139.64	4.579%	$146.0341	$146.03	$146.05	$146.00
Purchase #7	$48.83	11.119%	$54.2594	$54.26	$54.25	$54.30
7 purchase totals =	$908.14		$976.6846	$976.68	$976.65	$976.70