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	$46.58	11.739%	$52.048	$52.05	$52.05	$52.00
Purchase #2	$149.30	7.823%	$160.9797	$160.98	$161.00	$161.00
Purchase #3	$106.51	9.387%	$116.5081	$116.51	$116.50	$116.50
Purchase #4	$215.27	12.249%	$241.6384	$241.64	$241.65	$241.60
Purchase #5	$96.58	4.222%	$100.6576	$100.66	$100.65	$100.70
Purchase #6	$127.54	7.768%	$137.4473	$137.45	$137.45	$137.40
Purchase #7	$232.77	10.262%	$256.6569	$256.66	$256.65	$256.70
7 purchase totals =	$974.55		$1,065.9360	$1,065.95	$1,065.95	$1,065.90