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	$136.88	7.500%	$147.146	$147.15	$147.15	$147.10
Purchase #2	$155.84	5.866%	$164.9816	$164.98	$165.00	$165.00
Purchase #3	$166.80	12.463%	$187.5883	$187.59	$187.60	$187.60
Purchase #4	$119.90	10.200%	$132.1298	$132.13	$132.15	$132.10
Purchase #5	$81.37	5.481%	$85.8299	$85.83	$85.85	$85.80
Purchase #6	$144.35	4.269%	$150.5123	$150.51	$150.50	$150.50
Purchase #7	$223.46	11.177%	$248.4361	$248.44	$248.45	$248.40
7 purchase totals =	$1,028.60		$1,116.6240	$1,116.63	$1,116.70	$1,116.50