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	$192.95	10.735%	$213.6632	$213.66	$213.65	$213.70
Purchase #2	$130.34	12.488%	$146.6169	$146.62	$146.60	$146.60
Purchase #3	$11.29	3.266%	$11.6587	$11.66	$11.65	$11.70
Purchase #4	$123.77	3.128%	$127.6415	$127.64	$127.65	$127.60
Purchase #5	$118.45	5.509%	$124.9754	$124.98	$125.00	$125.00
Purchase #6	$166.89	4.152%	$173.8193	$173.82	$173.80	$173.80
Purchase #7	$36.82	5.691%	$38.9154	$38.92	$38.90	$38.90
7 purchase totals =	$780.51		$837.2904	$837.30	$837.25	$837.30