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	$192.40	6.657%	$205.2081	$205.21	$205.20	$205.20
Purchase #2	$101.54	5.545%	$107.1704	$107.17	$107.15	$107.20
Purchase #3	$162.52	12.290%	$182.4937	$182.49	$182.50	$182.50
Purchase #4	$200.87	9.777%	$220.5091	$220.51	$220.50	$220.50
Purchase #5	$59.54	10.717%	$65.9209	$65.92	$65.90	$65.90
Purchase #6	$169.60	12.763%	$191.246	$191.25	$191.25	$191.20
Purchase #7	$120.46	5.805%	$127.4527	$127.45	$127.45	$127.50
7 purchase totals =	$1,006.93		$1,100.0009	$1,100.00	$1,099.95	$1,100.00