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	$87.61	3.717%	$90.8665	$90.87	$90.85	$90.90
Purchase #2	$25.71	7.798%	$27.7149	$27.71	$27.70	$27.70
Purchase #3	$81.79	4.117%	$85.1573	$85.16	$85.15	$85.20
Purchase #4	$163.57	13.629%	$185.863	$185.86	$185.85	$185.90
Purchase #5	$62.46	5.353%	$65.8035	$65.80	$65.80	$65.80
Purchase #6	$185.45	12.286%	$208.2344	$208.23	$208.25	$208.20
Purchase #7	$152.79	6.384%	$162.5441	$162.54	$162.55	$162.50
7 purchase totals =	$759.38		$826.1837	$826.17	$826.15	$826.20