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	$84.63	5.369%	$89.1738	$89.17	$89.15	$89.20
Purchase #2	$93.71	11.777%	$104.7462	$104.75	$104.75	$104.70
Purchase #3	$75.84	7.314%	$81.3869	$81.39	$81.40	$81.40
Purchase #4	$222.94	13.525%	$253.0926	$253.09	$253.10	$253.10
Purchase #5	$152.72	3.785%	$158.5005	$158.50	$158.50	$158.50
Purchase #6	$91.92	8.103%	$99.3683	$99.37	$99.35	$99.40
Purchase #7	$113.99	8.439%	$123.6096	$123.61	$123.60	$123.60
7 purchase totals =	$835.75		$909.8779	$909.88	$909.85	$909.90