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	$65.67	7.848%	$70.8238	$70.82	$70.80	$70.80
Purchase #2	$241.69	5.723%	$255.5219	$255.52	$255.50	$255.50
Purchase #3	$41.25	7.668%	$44.4131	$44.41	$44.40	$44.40
Purchase #4	$152.77	5.212%	$160.7324	$160.73	$160.75	$160.70
Purchase #5	$186.49	6.683%	$198.9531	$198.95	$198.95	$199.00
Purchase #6	$235.64	6.787%	$251.6329	$251.63	$251.65	$251.60
Purchase #7	$110.98	11.594%	$123.847	$123.85	$123.85	$123.80
7 purchase totals =	$1,034.49		$1,105.9242	$1,105.91	$1,105.90	$1,105.80