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	$82.77	4.523%	$86.5137	$86.51	$86.50	$86.50
Purchase #2	$234.94	11.784%	$262.6253	$262.63	$262.65	$262.60
Purchase #3	$67.86	5.610%	$71.6669	$71.67	$71.65	$71.70
Purchase #4	$204.38	6.406%	$217.4726	$217.47	$217.45	$217.50
Purchase #5	$145.46	5.811%	$153.9127	$153.91	$153.90	$153.90
Purchase #6	$15.83	12.323%	$17.7807	$17.78	$17.80	$17.80
Purchase #7	$166.87	10.773%	$184.8469	$184.85	$184.85	$184.80
7 purchase totals =	$918.11		$994.8188	$994.82	$994.80	$994.80