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	$101.86	3.588%	$105.5147	$105.51	$105.50	$105.50
Purchase #2	$171.46	4.387%	$178.982	$178.98	$179.00	$179.00
Purchase #3	$83.55	3.540%	$86.5077	$86.51	$86.50	$86.50
Purchase #4	$190.64	12.559%	$214.5825	$214.58	$214.60	$214.60
Purchase #5	$210.52	11.387%	$234.4919	$234.49	$234.50	$234.50
Purchase #6	$155.95	11.862%	$174.4488	$174.45	$174.45	$174.40
Purchase #7	$66.54	11.427%	$74.1435	$74.14	$74.15	$74.10
7 purchase totals =	$980.52		$1,068.6711	$1,068.66	$1,068.70	$1,068.60