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	$102.53	3.167%	$105.7771	$105.78	$105.80	$105.80
Purchase #2	$19.28	6.204%	$20.4761	$20.48	$20.50	$20.50
Purchase #3	$156.35	3.513%	$161.8426	$161.84	$161.85	$161.80
Purchase #4	$113.29	8.381%	$122.7848	$122.78	$122.80	$122.80
Purchase #5	$80.94	7.131%	$86.7118	$86.71	$86.70	$86.70
Purchase #6	$87.58	6.873%	$93.5994	$93.60	$93.60	$93.60
Purchase #7	$85.86	3.842%	$89.1587	$89.16	$89.15	$89.20
7 purchase totals =	$645.83		$680.3505	$680.35	$680.40	$680.40