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	$104.28	7.139%	$111.7245	$111.72	$111.70	$111.70
Purchase #2	$60.55	8.377%	$65.6223	$65.62	$65.60	$65.60
Purchase #3	$104.73	7.834%	$112.9345	$112.93	$112.95	$112.90
Purchase #4	$180.69	13.650%	$205.3542	$205.35	$205.35	$205.40
Purchase #5	$176.48	13.746%	$200.7389	$200.74	$200.75	$200.70
Purchase #6	$110.44	7.634%	$118.871	$118.87	$118.85	$118.90
Purchase #7	$64.51	13.102%	$72.9621	$72.96	$72.95	$73.00
7 purchase totals =	$801.68		$888.2075	$888.19	$888.15	$888.20