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	$68.95	3.686%	$71.4915	$71.49	$71.50	$71.50
Purchase #2	$142.84	11.230%	$158.8809	$158.88	$158.90	$158.90
Purchase #3	$157.36	13.485%	$178.58	$178.58	$178.60	$178.60
Purchase #4	$95.79	6.781%	$102.2855	$102.29	$102.30	$102.30
Purchase #5	$242.67	13.848%	$276.2749	$276.27	$276.25	$276.30
Purchase #6	$145.71	8.845%	$158.598	$158.60	$158.60	$158.60
Purchase #7	$145.46	13.599%	$165.2411	$165.24	$165.25	$165.20
7 purchase totals =	$998.78		$1,111.3519	$1,111.35	$1,111.40	$1,111.40