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	$85.42	6.449%	$90.9287	$90.93	$90.95	$90.90
Purchase #2	$31.58	7.670%	$34.0022	$34.00	$34.00	$34.00
Purchase #3	$87.46	3.439%	$90.4677	$90.47	$90.45	$90.50
Purchase #4	$15.47	8.718%	$16.8187	$16.82	$16.80	$16.80
Purchase #5	$70.56	10.377%	$77.882	$77.88	$77.90	$77.90
Purchase #6	$238.64	3.865%	$247.8634	$247.86	$247.85	$247.90
Purchase #7	$25.58	6.655%	$27.2823	$27.28	$27.30	$27.30
7 purchase totals =	$554.71		$585.2450	$585.24	$585.25	$585.30