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	$121.38	5.109%	$127.5813	$127.58	$127.60	$127.60
Purchase #2	$110.28	5.596%	$116.4513	$116.45	$116.45	$116.50
Purchase #3	$188.57	13.409%	$213.8554	$213.86	$213.85	$213.90
Purchase #4	$119.42	10.459%	$131.9101	$131.91	$131.90	$131.90
Purchase #5	$238.61	6.513%	$254.1507	$254.15	$254.15	$254.20
Purchase #6	$146.48	11.521%	$163.356	$163.36	$163.35	$163.40
Purchase #7	$128.50	7.423%	$138.0386	$138.04	$138.05	$138.00
7 purchase totals =	$1,053.24		$1,145.3434	$1,145.35	$1,145.35	$1,145.50