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	$53.50	8.646%	$58.1256	$58.13	$58.15	$58.10
Purchase #2	$184.52	4.146%	$192.1702	$192.17	$192.15	$192.20
Purchase #3	$176.54	6.564%	$188.1281	$188.13	$188.15	$188.10
Purchase #4	$52.45	5.705%	$55.4423	$55.44	$55.45	$55.40
Purchase #5	$153.91	12.649%	$173.3781	$173.38	$173.40	$173.40
Purchase #6	$59.71	9.290%	$65.2571	$65.26	$65.25	$65.30
Purchase #7	$104.66	6.485%	$111.4472	$111.45	$111.45	$111.40
7 purchase totals =	$785.29		$843.9486	$843.96	$844.00	$843.90