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	$110.32	8.298%	$119.4744	$119.47	$119.45	$119.50
Purchase #2	$115.56	9.157%	$126.1418	$126.14	$126.15	$126.10
Purchase #3	$90.39	9.874%	$99.3151	$99.32	$99.30	$99.30
Purchase #4	$232.63	10.313%	$256.6211	$256.62	$256.60	$256.60
Purchase #5	$231.27	13.421%	$262.3087	$262.31	$262.30	$262.30
Purchase #6	$112.77	3.285%	$116.4745	$116.47	$116.45	$116.50
Purchase #7	$47.50	5.667%	$50.1918	$50.19	$50.20	$50.20
7 purchase totals =	$940.44		$1,030.5274	$1,030.52	$1,030.45	$1,030.50