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	$102.38	3.271%	$105.7288	$105.73	$105.75	$105.70
Purchase #2	$134.78	4.319%	$140.6011	$140.60	$140.60	$140.60
Purchase #3	$191.73	9.663%	$210.2569	$210.26	$210.25	$210.30
Purchase #4	$105.35	6.584%	$112.2862	$112.29	$112.30	$112.30
Purchase #5	$93.74	13.154%	$106.0706	$106.07	$106.05	$106.10
Purchase #6	$8.98	9.241%	$9.8098	$9.81	$9.80	$9.80
Purchase #7	$101.56	10.162%	$111.8805	$111.88	$111.90	$111.90
7 purchase totals =	$738.52		$796.6339	$796.64	$796.65	$796.70