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	$168.32	7.269%	$180.5552	$180.56	$180.55	$180.60
Purchase #2	$208.78	3.587%	$216.2689	$216.27	$216.25	$216.30
Purchase #3	$92.53	8.238%	$100.1526	$100.15	$100.15	$100.20
Purchase #4	$204.88	8.784%	$222.8767	$222.88	$222.90	$222.90
Purchase #5	$216.60	5.706%	$228.9592	$228.96	$228.95	$229.00
Purchase #6	$60.44	6.180%	$64.1752	$64.18	$64.20	$64.20
Purchase #7	$119.90	4.142%	$124.8663	$124.87	$124.85	$124.90
7 purchase totals =	$1,071.45		$1,137.8541	$1,137.87	$1,137.85	$1,138.10