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	$79.54	9.298%	$86.9356	$86.94	$86.95	$86.90
Purchase #2	$124.69	10.633%	$137.9483	$137.95	$137.95	$137.90
Purchase #3	$222.81	4.784%	$233.4692	$233.47	$233.45	$233.50
Purchase #4	$59.87	11.562%	$66.7922	$66.79	$66.80	$66.80
Purchase #5	$98.55	11.531%	$109.9138	$109.91	$109.90	$109.90
Purchase #6	$42.40	3.449%	$43.8624	$43.86	$43.85	$43.90
Purchase #7	$216.58	9.467%	$237.0836	$237.08	$237.10	$237.10
7 purchase totals =	$844.44		$916.0051	$916.00	$916.00	$916.00