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	$146.92	3.110%	$151.4892	$151.49	$151.50	$151.50
Purchase #2	$133.93	9.660%	$146.8676	$146.87	$146.85	$146.90
Purchase #3	$91.89	10.387%	$101.4346	$101.43	$101.45	$101.40
Purchase #4	$164.59	4.514%	$172.0196	$172.02	$172.00	$172.00
Purchase #5	$33.82	13.217%	$38.29	$38.29	$38.30	$38.30
Purchase #6	$147.87	6.729%	$157.8202	$157.82	$157.80	$157.80
Purchase #7	$230.72	5.807%	$244.1179	$244.12	$244.10	$244.10
7 purchase totals =	$949.74		$1,012.0391	$1,012.04	$1,012.00	$1,012.00