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	$166.89	13.395%	$189.2449	$189.24	$189.25	$189.20
Purchase #2	$69.37	13.732%	$78.8959	$78.90	$78.90	$78.90
Purchase #3	$153.28	3.569%	$158.7506	$158.75	$158.75	$158.80
Purchase #4	$173.47	4.254%	$180.8494	$180.85	$180.85	$180.80
Purchase #5	$36.31	6.209%	$38.5645	$38.56	$38.55	$38.60
Purchase #6	$77.32	5.461%	$81.5424	$81.54	$81.55	$81.50
Purchase #7	$178.63	10.298%	$197.0253	$197.03	$197.05	$197.00
7 purchase totals =	$855.27		$924.8730	$924.87	$924.90	$924.80