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	$164.52	8.298%	$178.1719	$178.17	$178.15	$178.20
Purchase #2	$91.54	8.286%	$99.125	$99.13	$99.15	$99.10
Purchase #3	$129.39	10.197%	$142.5839	$142.58	$142.60	$142.60
Purchase #4	$72.71	12.507%	$81.8038	$81.80	$81.80	$81.80
Purchase #5	$248.63	10.422%	$274.5422	$274.54	$274.55	$274.50
Purchase #6	$60.78	6.369%	$64.6511	$64.65	$64.65	$64.70
Purchase #7	$153.77	10.731%	$170.2711	$170.27	$170.25	$170.30
7 purchase totals =	$921.34		$1,011.1490	$1,011.14	$1,011.15	$1,011.20