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	$106.69	7.539%	$114.7334	$114.73	$114.75	$114.70
Purchase #2	$36.78	5.578%	$38.8316	$38.83	$38.85	$38.80
Purchase #3	$141.64	5.610%	$149.586	$149.59	$149.60	$149.60
Purchase #4	$56.77	4.577%	$59.3684	$59.37	$59.35	$59.40
Purchase #5	$139.53	13.825%	$158.82	$158.82	$158.80	$158.80
Purchase #6	$45.28	4.650%	$47.3855	$47.39	$47.40	$47.40
Purchase #7	$87.98	10.241%	$96.99	$96.99	$97.00	$97.00
7 purchase totals =	$614.67		$665.7149	$665.72	$665.75	$665.70