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	$127.26	13.696%	$144.6895	$144.69	$144.70	$144.70
Purchase #2	$146.62	5.397%	$154.5331	$154.53	$154.55	$154.50
Purchase #3	$220.65	8.304%	$238.9728	$238.97	$238.95	$239.00
Purchase #4	$209.61	8.474%	$227.3724	$227.37	$227.35	$227.40
Purchase #5	$148.58	11.605%	$165.8227	$165.82	$165.80	$165.80
Purchase #6	$103.94	5.447%	$109.6016	$109.60	$109.60	$109.60
Purchase #7	$113.31	12.578%	$127.5621	$127.56	$127.55	$127.60
7 purchase totals =	$1,069.97		$1,168.5542	$1,168.54	$1,168.50	$1,168.60