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	$159.58	13.521%	$181.1568	$181.16	$181.15	$181.20
Purchase #2	$130.72	10.511%	$144.46	$144.46	$144.45	$144.50
Purchase #3	$44.71	4.336%	$46.6486	$46.65	$46.65	$46.60
Purchase #4	$240.61	10.228%	$265.2196	$265.22	$265.20	$265.20
Purchase #5	$109.88	9.259%	$120.0538	$120.05	$120.05	$120.10
Purchase #6	$90.29	3.549%	$93.4944	$93.49	$93.50	$93.50
Purchase #7	$158.68	4.272%	$165.4588	$165.46	$165.45	$165.50
7 purchase totals =	$934.47		$1,016.4920	$1,016.49	$1,016.45	$1,016.60