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	$112.41	4.163%	$117.0896	$117.09	$117.10	$117.10
Purchase #2	$29.46	3.658%	$30.5376	$30.54	$30.55	$30.50
Purchase #3	$126.52	8.369%	$137.1085	$137.11	$137.10	$137.10
Purchase #4	$31.60	5.366%	$33.2957	$33.30	$33.30	$33.30
Purchase #5	$106.61	4.181%	$111.0674	$111.07	$111.05	$111.10
Purchase #6	$154.83	12.791%	$174.6343	$174.63	$174.65	$174.60
Purchase #7	$123.40	13.756%	$140.3749	$140.37	$140.35	$140.40
7 purchase totals =	$684.83		$744.1080	$744.11	$744.10	$744.10