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	$174.78	7.843%	$188.488	$188.49	$188.50	$188.50
Purchase #2	$70.81	4.845%	$74.2407	$74.24	$74.25	$74.20
Purchase #3	$58.69	6.403%	$62.4479	$62.45	$62.45	$62.40
Purchase #4	$132.42	9.593%	$145.1231	$145.12	$145.10	$145.10
Purchase #5	$204.52	11.279%	$227.5878	$227.59	$227.60	$227.60
Purchase #6	$242.48	13.219%	$274.5334	$274.53	$274.55	$274.50
Purchase #7	$72.87	5.845%	$77.1293	$77.13	$77.15	$77.10
7 purchase totals =	$956.57		$1,049.5502	$1,049.55	$1,049.60	$1,049.40