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	$119.62	6.306%	$127.1632	$127.16	$127.15	$127.20
Purchase #2	$24.31	13.561%	$27.6067	$27.61	$27.60	$27.60
Purchase #3	$82.65	4.180%	$86.1048	$86.10	$86.10	$86.10
Purchase #4	$199.93	10.128%	$220.1789	$220.18	$220.20	$220.20
Purchase #5	$141.41	3.351%	$146.1486	$146.15	$146.15	$146.10
Purchase #6	$85.80	6.734%	$91.5778	$91.58	$91.60	$91.60
Purchase #7	$67.96	7.287%	$72.9122	$72.91	$72.90	$72.90
7 purchase totals =	$721.68		$771.6922	$771.69	$771.70	$771.70