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	$116.34	9.745%	$127.6773	$127.68	$127.70	$127.70
Purchase #2	$91.85	3.791%	$95.332	$95.33	$95.35	$95.30
Purchase #3	$88.62	6.739%	$94.5921	$94.59	$94.60	$94.60
Purchase #4	$227.45	9.239%	$248.4641	$248.46	$248.45	$248.50
Purchase #5	$98.91	3.840%	$102.7081	$102.71	$102.70	$102.70
Purchase #6	$250.42	11.615%	$279.5063	$279.51	$279.50	$279.50
Purchase #7	$232.97	6.574%	$248.2854	$248.29	$248.30	$248.30
7 purchase totals =	$1,106.56		$1,196.5653	$1,196.57	$1,196.60	$1,196.60