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	$179.85	10.403%	$198.5598	$198.56	$198.55	$198.60
Purchase #2	$116.45	11.486%	$129.8254	$129.83	$129.85	$129.80
Purchase #3	$217.83	3.103%	$224.5893	$224.59	$224.60	$224.60
Purchase #4	$202.92	12.123%	$227.52	$227.52	$227.50	$227.50
Purchase #5	$148.67	10.413%	$164.151	$164.15	$164.15	$164.20
Purchase #6	$194.26	11.780%	$217.1438	$217.14	$217.15	$217.10
Purchase #7	$11.76	6.439%	$12.5172	$12.52	$12.50	$12.50
7 purchase totals =	$1,071.74		$1,174.3065	$1,174.31	$1,174.30	$1,174.30