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	$77.82	10.710%	$86.1545	$86.15	$86.15	$86.20
Purchase #2	$65.25	9.710%	$71.5858	$71.59	$71.60	$71.60
Purchase #3	$177.93	6.388%	$189.2962	$189.30	$189.30	$189.30
Purchase #4	$95.47	7.195%	$102.3391	$102.34	$102.35	$102.30
Purchase #5	$233.78	7.199%	$250.6098	$250.61	$250.60	$250.60
Purchase #6	$113.87	11.846%	$127.359	$127.36	$127.35	$127.40
Purchase #7	$226.56	8.838%	$246.5834	$246.58	$246.60	$246.60
7 purchase totals =	$990.68		$1,073.9278	$1,073.93	$1,073.95	$1,074.00