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	$172.71	11.213%	$192.076	$192.08	$192.10	$192.10
Purchase #2	$82.26	3.163%	$84.8619	$84.86	$84.85	$84.90
Purchase #3	$88.67	13.706%	$100.8231	$100.82	$100.80	$100.80
Purchase #4	$92.98	4.437%	$97.1055	$97.11	$97.10	$97.10
Purchase #5	$57.31	3.667%	$59.4116	$59.41	$59.40	$59.40
Purchase #6	$84.58	13.341%	$95.8638	$95.86	$95.85	$95.90
Purchase #7	$202.30	13.456%	$229.5215	$229.52	$229.50	$229.50
7 purchase totals =	$780.81		$859.6634	$859.66	$859.60	$859.70