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	$100.90	11.256%	$112.2573	$112.26	$112.25	$112.30
Purchase #2	$148.44	11.178%	$165.0326	$165.03	$165.05	$165.00
Purchase #3	$243.66	9.167%	$265.9963	$266.00	$266.00	$266.00
Purchase #4	$49.30	10.515%	$54.4839	$54.48	$54.50	$54.50
Purchase #5	$105.28	12.414%	$118.3495	$118.35	$118.35	$118.30
Purchase #6	$207.32	11.545%	$231.2551	$231.26	$231.25	$231.30
Purchase #7	$78.78	5.713%	$83.2807	$83.28	$83.30	$83.30
7 purchase totals =	$933.68		$1,030.6554	$1,030.66	$1,030.70	$1,030.70