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	$140.87	7.709%	$151.7297	$151.73	$151.75	$151.70
Purchase #2	$65.43	10.301%	$72.1699	$72.17	$72.15	$72.20
Purchase #3	$75.95	13.409%	$86.1341	$86.13	$86.15	$86.10
Purchase #4	$89.52	6.252%	$95.1168	$95.12	$95.10	$95.10
Purchase #5	$60.66	10.196%	$66.8449	$66.84	$66.85	$66.80
Purchase #6	$172.87	4.173%	$180.0839	$180.08	$180.10	$180.10
Purchase #7	$188.25	11.335%	$209.5881	$209.59	$209.60	$209.60
7 purchase totals =	$793.55		$861.6674	$861.66	$861.70	$861.60