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	$205.87	12.253%	$231.0953	$231.10	$231.10	$231.10
Purchase #2	$40.43	8.599%	$43.9066	$43.91	$43.90	$43.90
Purchase #3	$224.72	9.610%	$246.3156	$246.32	$246.30	$246.30
Purchase #4	$162.62	6.463%	$173.1301	$173.13	$173.15	$173.10
Purchase #5	$218.38	3.275%	$225.5319	$225.53	$225.55	$225.50
Purchase #6	$64.65	12.228%	$72.5554	$72.56	$72.55	$72.60
Purchase #7	$211.90	3.250%	$218.7868	$218.79	$218.80	$218.80
7 purchase totals =	$1,128.57		$1,211.3217	$1,211.34	$1,211.35	$1,211.30