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	$210.84	13.430%	$239.1558	$239.16	$239.15	$239.20
Purchase #2	$86.82	4.834%	$91.0169	$91.02	$91.00	$91.00
Purchase #3	$242.80	11.177%	$269.9378	$269.94	$269.95	$269.90
Purchase #4	$57.49	3.716%	$59.6263	$59.63	$59.65	$59.60
Purchase #5	$184.47	10.557%	$203.9445	$203.94	$203.95	$203.90
Purchase #6	$110.77	5.245%	$116.5799	$116.58	$116.60	$116.60
Purchase #7	$72.96	11.233%	$81.1556	$81.16	$81.15	$81.20
7 purchase totals =	$966.15		$1,061.4168	$1,061.43	$1,061.45	$1,061.40