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	$190.70	3.385%	$197.1552	$197.16	$197.15	$197.20
Purchase #2	$127.67	9.185%	$139.3965	$139.40	$139.40	$139.40
Purchase #3	$164.49	12.417%	$184.9147	$184.91	$184.90	$184.90
Purchase #4	$146.37	8.260%	$158.4602	$158.46	$158.45	$158.50
Purchase #5	$136.41	3.649%	$141.3876	$141.39	$141.40	$141.40
Purchase #6	$167.67	12.259%	$188.2247	$188.22	$188.20	$188.20
Purchase #7	$153.73	3.629%	$159.3089	$159.31	$159.30	$159.30
7 purchase totals =	$1,087.04		$1,168.8478	$1,168.85	$1,168.80	$1,168.90