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	$134.95	5.599%	$142.5059	$142.51	$142.50	$142.50
Purchase #2	$138.81	3.230%	$143.2936	$143.29	$143.30	$143.30
Purchase #3	$35.88	5.528%	$37.8634	$37.86	$37.85	$37.90
Purchase #4	$91.49	11.820%	$102.3041	$102.30	$102.30	$102.30
Purchase #5	$210.85	3.548%	$218.331	$218.33	$218.35	$218.30
Purchase #6	$135.93	4.246%	$141.7016	$141.70	$141.70	$141.70
Purchase #7	$54.52	12.501%	$61.3355	$61.34	$61.35	$61.30
7 purchase totals =	$802.43		$847.3351	$847.33	$847.35	$847.30