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	$41.82	7.755%	$45.0631	$45.06	$45.05	$45.10
Purchase #2	$9.97	3.427%	$10.3117	$10.31	$10.30	$10.30
Purchase #3	$176.57	7.196%	$189.276	$189.28	$189.30	$189.30
Purchase #4	$40.41	12.576%	$45.492	$45.49	$45.50	$45.50
Purchase #5	$127.66	13.577%	$144.9924	$144.99	$145.00	$145.00
Purchase #6	$183.90	4.155%	$191.541	$191.54	$191.55	$191.50
Purchase #7	$138.82	13.468%	$157.5163	$157.52	$157.50	$157.50
7 purchase totals =	$719.15		$784.1925	$784.19	$784.20	$784.20