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	$111.36	10.506%	$123.0595	$123.06	$123.05	$123.10
Purchase #2	$84.91	7.502%	$91.2799	$91.28	$91.30	$91.30
Purchase #3	$180.61	9.739%	$198.1996	$198.20	$198.20	$198.20
Purchase #4	$203.96	10.598%	$225.5757	$225.58	$225.60	$225.60
Purchase #5	$159.94	8.426%	$173.4165	$173.42	$173.40	$173.40
Purchase #6	$77.59	4.615%	$81.1708	$81.17	$81.15	$81.20
Purchase #7	$109.52	13.707%	$124.5319	$124.53	$124.55	$124.50
7 purchase totals =	$927.89		$1,017.2339	$1,017.24	$1,017.25	$1,017.30