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	$188.85	13.536%	$214.4127	$214.41	$214.40	$214.40
Purchase #2	$8.78	6.223%	$9.3264	$9.33	$9.35	$9.30
Purchase #3	$63.27	5.261%	$66.5986	$66.60	$66.60	$66.60
Purchase #4	$43.31	11.426%	$48.2586	$48.26	$48.25	$48.30
Purchase #5	$65.92	10.520%	$72.8548	$72.85	$72.85	$72.90
Purchase #6	$73.46	12.779%	$82.8475	$82.85	$82.85	$82.80
Purchase #7	$101.90	5.164%	$107.1621	$107.16	$107.15	$107.20
7 purchase totals =	$545.49		$601.4607	$601.46	$601.45	$601.50