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	$54.42	7.852%	$58.6931	$58.69	$58.70	$58.70
Purchase #2	$147.78	10.735%	$163.6442	$163.64	$163.65	$163.60
Purchase #3	$211.87	12.692%	$238.7605	$238.76	$238.75	$238.80
Purchase #4	$63.29	6.678%	$67.5165	$67.52	$67.50	$67.50
Purchase #5	$246.25	11.460%	$274.4703	$274.47	$274.45	$274.50
Purchase #6	$154.71	9.128%	$168.8319	$168.83	$168.85	$168.80
Purchase #7	$214.37	3.773%	$222.4582	$222.46	$222.45	$222.50
7 purchase totals =	$1,092.69		$1,194.3747	$1,194.37	$1,194.35	$1,194.40