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	$20.54	10.194%	$22.6338	$22.63	$22.65	$22.60
Purchase #2	$86.39	11.548%	$96.3663	$96.37	$96.35	$96.40
Purchase #3	$202.57	11.338%	$225.5374	$225.54	$225.55	$225.50
Purchase #4	$79.68	13.648%	$90.5547	$90.55	$90.55	$90.60
Purchase #5	$158.28	11.481%	$176.4521	$176.45	$176.45	$176.50
Purchase #6	$214.50	7.300%	$230.1585	$230.16	$230.15	$230.20
Purchase #7	$161.50	6.369%	$171.7859	$171.79	$171.80	$171.80
7 purchase totals =	$923.46		$1,013.4887	$1,013.49	$1,013.50	$1,013.60