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	$176.42	5.399%	$185.9449	$185.94	$185.95	$185.90
Purchase #2	$196.93	4.336%	$205.4689	$205.47	$205.45	$205.50
Purchase #3	$234.89	5.263%	$247.2523	$247.25	$247.25	$247.30
Purchase #4	$50.42	8.151%	$54.5297	$54.53	$54.55	$54.50
Purchase #5	$67.51	3.862%	$70.1172	$70.12	$70.10	$70.10
Purchase #6	$241.42	8.766%	$262.5829	$262.58	$262.60	$262.60
Purchase #7	$49.89	10.843%	$55.2996	$55.30	$55.30	$55.30
7 purchase totals =	$1,017.48		$1,081.1955	$1,081.19	$1,081.20	$1,081.20