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	$172.95	5.318%	$182.1475	$182.15	$182.15	$182.10
Purchase #2	$172.57	3.855%	$179.2226	$179.22	$179.20	$179.20
Purchase #3	$204.69	10.830%	$226.8579	$226.86	$226.85	$226.90
Purchase #4	$143.69	9.167%	$156.8621	$156.86	$156.85	$156.90
Purchase #5	$103.30	9.262%	$112.8676	$112.87	$112.85	$112.90
Purchase #6	$12.68	12.531%	$14.2689	$14.27	$14.25	$14.30
Purchase #7	$180.37	4.471%	$188.4343	$188.43	$188.45	$188.40
7 purchase totals =	$990.25		$1,060.6609	$1,060.66	$1,060.60	$1,060.70