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	$98.69	3.704%	$102.3455	$102.35	$102.35	$102.30
Purchase #2	$237.28	7.681%	$255.5055	$255.51	$255.50	$255.50
Purchase #3	$167.86	10.201%	$184.9834	$184.98	$185.00	$185.00
Purchase #4	$127.47	3.678%	$132.1583	$132.16	$132.15	$132.20
Purchase #5	$13.59	6.505%	$14.474	$14.47	$14.45	$14.50
Purchase #6	$203.83	8.118%	$220.3769	$220.38	$220.40	$220.40
Purchase #7	$37.38	11.497%	$41.6776	$41.68	$41.70	$41.70
7 purchase totals =	$886.10		$951.5212	$951.53	$951.55	$951.60