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	$152.96	9.168%	$166.9834	$166.98	$167.00	$167.00
Purchase #2	$72.57	9.569%	$79.5142	$79.51	$79.50	$79.50
Purchase #3	$179.39	11.365%	$199.7777	$199.78	$199.80	$199.80
Purchase #4	$42.35	13.408%	$48.0283	$48.03	$48.05	$48.00
Purchase #5	$86.71	13.335%	$98.2728	$98.27	$98.25	$98.30
Purchase #6	$101.50	10.216%	$111.8692	$111.87	$111.85	$111.90
Purchase #7	$51.97	6.245%	$55.2155	$55.22	$55.20	$55.20
7 purchase totals =	$687.45		$759.6611	$759.66	$759.65	$759.70