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	$168.42	3.303%	$173.9829	$173.98	$174.00	$174.00
Purchase #2	$159.87	12.181%	$179.3438	$179.34	$179.35	$179.30
Purchase #3	$152.68	13.256%	$172.9193	$172.92	$172.90	$172.90
Purchase #4	$64.42	11.135%	$71.5932	$71.59	$71.60	$71.60
Purchase #5	$232.43	8.456%	$252.0843	$252.08	$252.10	$252.10
Purchase #6	$68.27	3.284%	$70.512	$70.51	$70.50	$70.50
Purchase #7	$116.72	5.599%	$123.2552	$123.26	$123.25	$123.30
7 purchase totals =	$962.81		$1,043.6907	$1,043.68	$1,043.70	$1,043.70