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	$126.29	4.481%	$131.9491	$131.95	$131.95	$131.90
Purchase #2	$144.32	6.233%	$153.3155	$153.32	$153.30	$153.30
Purchase #3	$40.83	10.581%	$45.1502	$45.15	$45.15	$45.20
Purchase #4	$236.53	3.162%	$244.0091	$244.01	$244.00	$244.00
Purchase #5	$175.53	5.788%	$185.6897	$185.69	$185.70	$185.70
Purchase #6	$46.40	10.142%	$51.1059	$51.11	$51.10	$51.10
Purchase #7	$51.47	3.248%	$53.1417	$53.14	$53.15	$53.10
7 purchase totals =	$821.37		$864.3612	$864.37	$864.35	$864.30