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	$182.77	3.828%	$189.7664	$189.77	$189.75	$189.80
Purchase #2	$197.89	3.857%	$205.5226	$205.52	$205.50	$205.50
Purchase #3	$221.59	4.665%	$231.9272	$231.93	$231.95	$231.90
Purchase #4	$36.48	10.710%	$40.387	$40.39	$40.40	$40.40
Purchase #5	$83.47	12.832%	$94.1809	$94.18	$94.20	$94.20
Purchase #6	$244.92	4.444%	$255.8042	$255.80	$255.80	$255.80
Purchase #7	$50.27	6.588%	$53.5818	$53.58	$53.60	$53.60
7 purchase totals =	$1,017.39		$1,071.1701	$1,071.17	$1,071.20	$1,071.20