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	$164.50	11.492%	$183.4043	$183.40	$183.40	$183.40
Purchase #2	$124.82	10.561%	$138.0022	$138.00	$138.00	$138.00
Purchase #3	$173.48	12.479%	$195.1286	$195.13	$195.15	$195.10
Purchase #4	$50.41	8.633%	$54.7619	$54.76	$54.75	$54.80
Purchase #5	$70.77	11.191%	$78.6899	$78.69	$78.70	$78.70
Purchase #6	$250.58	12.847%	$282.772	$282.77	$282.75	$282.80
Purchase #7	$40.45	4.834%	$42.4054	$42.41	$42.40	$42.40
7 purchase totals =	$875.01		$975.1643	$975.16	$975.15	$975.20