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	$171.30	5.727%	$181.1104	$181.11	$181.10	$181.10
Purchase #2	$80.78	13.250%	$91.4834	$91.48	$91.50	$91.50
Purchase #3	$53.40	3.359%	$55.1937	$55.19	$55.20	$55.20
Purchase #4	$153.51	3.847%	$159.4155	$159.42	$159.40	$159.40
Purchase #5	$222.55	8.673%	$241.8518	$241.85	$241.85	$241.90
Purchase #6	$100.27	4.190%	$104.4713	$104.47	$104.45	$104.50
Purchase #7	$127.28	9.766%	$139.7102	$139.71	$139.70	$139.70
7 purchase totals =	$909.09		$973.2363	$973.23	$973.20	$973.30