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	$208.30	11.185%	$231.5984	$231.60	$231.60	$231.60
Purchase #2	$69.77	10.855%	$77.3435	$77.34	$77.35	$77.30
Purchase #3	$98.31	7.112%	$105.3018	$105.30	$105.30	$105.30
Purchase #4	$64.91	8.134%	$70.1898	$70.19	$70.20	$70.20
Purchase #5	$25.97	7.371%	$27.8842	$27.88	$27.90	$27.90
Purchase #6	$66.83	8.601%	$72.578	$72.58	$72.60	$72.60
Purchase #7	$94.49	13.833%	$107.5608	$107.56	$107.55	$107.60
7 purchase totals =	$628.58		$692.4565	$692.45	$692.50	$692.50