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	$220.30	9.664%	$241.5898	$241.59	$241.60	$241.60
Purchase #2	$98.97	4.298%	$103.2237	$103.22	$103.20	$103.20
Purchase #3	$86.75	6.873%	$92.7123	$92.71	$92.70	$92.70
Purchase #4	$108.52	13.524%	$123.1962	$123.20	$123.20	$123.20
Purchase #5	$142.32	4.189%	$148.2818	$148.28	$148.30	$148.30
Purchase #6	$55.49	3.240%	$57.2879	$57.29	$57.30	$57.30
Purchase #7	$208.80	13.560%	$237.1133	$237.11	$237.10	$237.10
7 purchase totals =	$921.15		$1,003.4050	$1,003.40	$1,003.40	$1,003.40