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	$187.28	4.196%	$195.1383	$195.14	$195.15	$195.10
Purchase #2	$28.91	3.137%	$29.8169	$29.82	$29.80	$29.80
Purchase #3	$184.65	8.523%	$200.3877	$200.39	$200.40	$200.40
Purchase #4	$225.81	13.690%	$256.7234	$256.72	$256.70	$256.70
Purchase #5	$105.90	10.650%	$117.1784	$117.18	$117.20	$117.20
Purchase #6	$78.50	11.589%	$87.5974	$87.60	$87.60	$87.60
Purchase #7	$159.77	3.113%	$164.7436	$164.74	$164.75	$164.70
7 purchase totals =	$970.82		$1,051.5857	$1,051.59	$1,051.60	$1,051.50