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	$145.52	13.790%	$165.5872	$165.59	$165.60	$165.60
Purchase #2	$152.37	11.430%	$169.7859	$169.79	$169.80	$169.80
Purchase #3	$116.74	11.727%	$130.4301	$130.43	$130.45	$130.40
Purchase #4	$209.86	7.394%	$225.377	$225.38	$225.40	$225.40
Purchase #5	$189.34	7.849%	$204.2013	$204.20	$204.20	$204.20
Purchase #6	$193.27	6.467%	$205.7688	$205.77	$205.75	$205.80
Purchase #7	$9.28	9.150%	$10.1291	$10.13	$10.15	$10.10
7 purchase totals =	$1,016.38		$1,111.2794	$1,111.29	$1,111.35	$1,111.30