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	$158.39	11.445%	$176.5177	$176.52	$176.50	$176.50
Purchase #2	$72.71	13.117%	$82.2474	$82.25	$82.25	$82.20
Purchase #3	$215.85	6.117%	$229.0535	$229.05	$229.05	$229.10
Purchase #4	$103.81	7.270%	$111.357	$111.36	$111.35	$111.40
Purchase #5	$94.57	11.607%	$105.5467	$105.55	$105.55	$105.50
Purchase #6	$225.95	5.154%	$237.5955	$237.60	$237.60	$237.60
Purchase #7	$171.99	8.801%	$187.1268	$187.13	$187.15	$187.10
7 purchase totals =	$1,043.27		$1,129.4446	$1,129.46	$1,129.45	$1,129.40