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	$135.32	5.792%	$143.1577	$143.16	$143.15	$143.20
Purchase #2	$105.66	7.466%	$113.5486	$113.55	$113.55	$113.50
Purchase #3	$152.55	13.132%	$172.5829	$172.58	$172.60	$172.60
Purchase #4	$59.29	13.596%	$67.3511	$67.35	$67.35	$67.40
Purchase #5	$67.43	11.555%	$75.2215	$75.22	$75.20	$75.20
Purchase #6	$205.33	5.822%	$217.2843	$217.28	$217.30	$217.30
Purchase #7	$134.34	8.213%	$145.3733	$145.37	$145.35	$145.40
7 purchase totals =	$859.92		$934.5194	$934.51	$934.50	$934.60