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	$185.80	6.153%	$197.2323	$197.23	$197.25	$197.20
Purchase #2	$155.83	6.526%	$165.9995	$166.00	$166.00	$166.00
Purchase #3	$121.93	4.305%	$127.1791	$127.18	$127.20	$127.20
Purchase #4	$100.37	12.401%	$112.8169	$112.82	$112.80	$112.80
Purchase #5	$238.95	13.634%	$271.5284	$271.53	$271.55	$271.50
Purchase #6	$71.48	10.455%	$78.9532	$78.95	$78.95	$79.00
Purchase #7	$86.78	5.365%	$91.4357	$91.44	$91.45	$91.40
7 purchase totals =	$961.14		$1,045.1451	$1,045.15	$1,045.20	$1,045.10