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	$42.91	6.217%	$45.5777	$45.58	$45.60	$45.60
Purchase #2	$158.25	9.375%	$173.0859	$173.09	$173.10	$173.10
Purchase #3	$172.42	10.424%	$190.3931	$190.39	$190.40	$190.40
Purchase #4	$212.52	8.165%	$229.8723	$229.87	$229.85	$229.90
Purchase #5	$210.43	10.189%	$231.8707	$231.87	$231.85	$231.90
Purchase #6	$226.66	3.644%	$234.9195	$234.92	$234.90	$234.90
Purchase #7	$36.97	8.245%	$40.0182	$40.02	$40.00	$40.00
7 purchase totals =	$1,060.16		$1,145.7374	$1,145.74	$1,145.70	$1,145.80