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	$75.48	13.411%	$85.6026	$85.60	$85.60	$85.60
Purchase #2	$58.57	7.277%	$62.8321	$62.83	$62.85	$62.80
Purchase #3	$47.42	12.109%	$53.1621	$53.16	$53.15	$53.20
Purchase #4	$203.53	6.358%	$216.4704	$216.47	$216.45	$216.50
Purchase #5	$70.97	8.634%	$77.0975	$77.10	$77.10	$77.10
Purchase #6	$25.52	7.797%	$27.5098	$27.51	$27.50	$27.50
Purchase #7	$58.27	10.489%	$64.3819	$64.38	$64.40	$64.40
7 purchase totals =	$539.76		$587.0564	$587.05	$587.05	$587.10