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	$137.68	6.366%	$146.4447	$146.44	$146.45	$146.40
Purchase #2	$93.84	7.188%	$100.5852	$100.59	$100.60	$100.60
Purchase #3	$128.90	8.582%	$139.9622	$139.96	$139.95	$140.00
Purchase #4	$185.66	6.693%	$198.0862	$198.09	$198.10	$198.10
Purchase #5	$145.64	3.628%	$150.9238	$150.92	$150.90	$150.90
Purchase #6	$228.55	10.547%	$252.6552	$252.66	$252.65	$252.70
Purchase #7	$105.56	10.799%	$116.9594	$116.96	$116.95	$117.00
7 purchase totals =	$1,025.83		$1,105.6167	$1,105.62	$1,105.60	$1,105.70