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	$103.98	6.534%	$110.7741	$110.77	$110.75	$110.80
Purchase #2	$86.52	11.294%	$96.2916	$96.29	$96.30	$96.30
Purchase #3	$98.36	13.221%	$111.3642	$111.36	$111.35	$111.40
Purchase #4	$99.52	10.683%	$110.1517	$110.15	$110.15	$110.20
Purchase #5	$31.79	4.520%	$33.2269	$33.23	$33.25	$33.20
Purchase #6	$92.70	8.583%	$100.6564	$100.66	$100.65	$100.70
Purchase #7	$140.91	11.734%	$157.4444	$157.44	$157.45	$157.40
7 purchase totals =	$653.78		$719.9093	$719.90	$719.90	$720.00