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	$172.76	7.338%	$185.4371	$185.44	$185.45	$185.40
Purchase #2	$225.32	3.676%	$233.6028	$233.60	$233.60	$233.60
Purchase #3	$196.89	13.857%	$224.173	$224.17	$224.15	$224.20
Purchase #4	$24.77	9.430%	$27.1058	$27.11	$27.10	$27.10
Purchase #5	$54.29	8.559%	$58.9367	$58.94	$58.95	$58.90
Purchase #6	$129.54	12.694%	$145.9838	$145.98	$146.00	$146.00
Purchase #7	$66.46	8.532%	$72.1304	$72.13	$72.15	$72.10
7 purchase totals =	$870.03		$947.3696	$947.37	$947.40	$947.30