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	$173.39	10.353%	$191.3411	$191.34	$191.35	$191.30
Purchase #2	$218.53	13.214%	$247.4066	$247.41	$247.40	$247.40
Purchase #3	$226.32	11.744%	$252.899	$252.90	$252.90	$252.90
Purchase #4	$83.32	7.370%	$89.4607	$89.46	$89.45	$89.50
Purchase #5	$112.48	4.707%	$117.7744	$117.77	$117.75	$117.80
Purchase #6	$120.51	5.558%	$127.2079	$127.21	$127.20	$127.20
Purchase #7	$218.51	12.813%	$246.5077	$246.51	$246.50	$246.50
7 purchase totals =	$1,153.06		$1,272.5974	$1,272.60	$1,272.55	$1,272.60