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	$49.54	9.765%	$54.3776	$54.38	$54.40	$54.40
Purchase #2	$137.55	5.118%	$144.5898	$144.59	$144.60	$144.60
Purchase #3	$163.31	5.577%	$172.4178	$172.42	$172.40	$172.40
Purchase #4	$209.49	8.776%	$227.8748	$227.87	$227.85	$227.90
Purchase #5	$58.38	13.780%	$66.4248	$66.42	$66.40	$66.40
Purchase #6	$210.70	11.671%	$235.2908	$235.29	$235.30	$235.30
Purchase #7	$183.38	5.203%	$192.9213	$192.92	$192.90	$192.90
7 purchase totals =	$1,012.35		$1,093.8969	$1,093.89	$1,093.85	$1,093.90