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	$159.53	11.193%	$177.3862	$177.39	$177.40	$177.40
Purchase #2	$156.40	10.773%	$173.249	$173.25	$173.25	$173.20
Purchase #3	$72.29	13.812%	$82.2747	$82.27	$82.25	$82.30
Purchase #4	$134.58	5.425%	$141.881	$141.88	$141.90	$141.90
Purchase #5	$26.68	11.865%	$29.8456	$29.85	$29.85	$29.80
Purchase #6	$55.39	10.463%	$61.1855	$61.19	$61.20	$61.20
Purchase #7	$112.60	5.796%	$119.1263	$119.13	$119.15	$119.10
7 purchase totals =	$717.47		$784.9483	$784.96	$785.00	$784.90