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	$205.39	9.451%	$224.8014	$224.80	$224.80	$224.80
Purchase #2	$174.34	12.591%	$196.2911	$196.29	$196.30	$196.30
Purchase #3	$226.45	10.774%	$250.8477	$250.85	$250.85	$250.80
Purchase #4	$230.38	3.662%	$238.8165	$238.82	$238.80	$238.80
Purchase #5	$96.32	6.376%	$102.4614	$102.46	$102.45	$102.50
Purchase #6	$190.42	13.252%	$215.6545	$215.65	$215.65	$215.70
Purchase #7	$173.67	13.443%	$197.0165	$197.02	$197.00	$197.00
7 purchase totals =	$1,296.97		$1,425.8891	$1,425.89	$1,425.85	$1,425.90