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	$232.75	11.814%	$260.2471	$260.25	$260.25	$260.20
Purchase #2	$102.91	8.368%	$111.5215	$111.52	$111.50	$111.50
Purchase #3	$10.36	5.552%	$10.9352	$10.94	$10.95	$10.90
Purchase #4	$75.81	13.251%	$85.8556	$85.86	$85.85	$85.90
Purchase #5	$157.44	13.372%	$178.4929	$178.49	$178.50	$178.50
Purchase #6	$133.72	3.782%	$138.7773	$138.78	$138.80	$138.80
Purchase #7	$242.25	13.692%	$275.4189	$275.42	$275.40	$275.40
7 purchase totals =	$955.24		$1,061.2485	$1,061.26	$1,061.25	$1,061.20