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	$146.92	12.197%	$164.8398	$164.84	$164.85	$164.80
Purchase #2	$60.38	7.436%	$64.8699	$64.87	$64.85	$64.90
Purchase #3	$98.37	13.446%	$111.5968	$111.60	$111.60	$111.60
Purchase #4	$106.28	6.537%	$113.2275	$113.23	$113.25	$113.20
Purchase #5	$137.65	6.401%	$146.461	$146.46	$146.45	$146.50
Purchase #6	$25.27	12.235%	$28.3618	$28.36	$28.35	$28.40
Purchase #7	$139.66	6.798%	$149.1541	$149.15	$149.15	$149.20
7 purchase totals =	$714.53		$778.5109	$778.51	$778.50	$778.60