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	$103.87	11.545%	$115.8618	$115.86	$115.85	$115.90
Purchase #2	$130.88	10.816%	$145.036	$145.04	$145.05	$145.00
Purchase #3	$136.73	7.118%	$146.4624	$146.46	$146.45	$146.50
Purchase #4	$173.96	10.325%	$191.9214	$191.92	$191.90	$191.90
Purchase #5	$228.46	10.564%	$252.5945	$252.59	$252.60	$252.60
Purchase #6	$95.30	4.379%	$99.4732	$99.47	$99.45	$99.50
Purchase #7	$99.48	5.340%	$104.7922	$104.79	$104.80	$104.80
7 purchase totals =	$968.68		$1,056.1415	$1,056.13	$1,056.10	$1,056.20