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	$189.44	13.447%	$214.914	$214.91	$214.90	$214.90
Purchase #2	$66.47	7.378%	$71.3742	$71.37	$71.35	$71.40
Purchase #3	$221.33	6.757%	$236.2853	$236.29	$236.30	$236.30
Purchase #4	$149.54	10.248%	$164.8649	$164.86	$164.85	$164.90
Purchase #5	$250.60	5.517%	$264.4256	$264.43	$264.45	$264.40
Purchase #6	$101.58	11.236%	$112.9935	$112.99	$113.00	$113.00
Purchase #7	$99.96	3.699%	$103.6575	$103.66	$103.65	$103.70
7 purchase totals =	$1,078.92		$1,168.5150	$1,168.51	$1,168.50	$1,168.60