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	$66.43	4.602%	$69.4871	$69.49	$69.50	$69.50
Purchase #2	$111.97	3.746%	$116.1644	$116.16	$116.15	$116.20
Purchase #3	$165.58	6.620%	$176.5414	$176.54	$176.55	$176.50
Purchase #4	$32.85	13.392%	$37.2493	$37.25	$37.25	$37.20
Purchase #5	$75.69	10.177%	$83.393	$83.39	$83.40	$83.40
Purchase #6	$81.73	5.572%	$86.284	$86.28	$86.30	$86.30
Purchase #7	$216.82	12.456%	$243.8271	$243.83	$243.85	$243.80
7 purchase totals =	$751.07		$812.9463	$812.94	$813.00	$812.90