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	$42.54	4.562%	$44.4807	$44.48	$44.50	$44.50
Purchase #2	$95.50	6.133%	$101.357	$101.36	$101.35	$101.40
Purchase #3	$112.47	3.739%	$116.6753	$116.68	$116.70	$116.70
Purchase #4	$147.88	3.484%	$153.0321	$153.03	$153.05	$153.00
Purchase #5	$65.33	9.392%	$71.4658	$71.47	$71.45	$71.50
Purchase #6	$43.45	4.216%	$45.2819	$45.28	$45.30	$45.30
Purchase #7	$103.27	10.784%	$114.4066	$114.41	$114.40	$114.40
7 purchase totals =	$610.44		$646.6994	$646.71	$646.75	$646.80