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	$119.53	3.191%	$123.3442	$123.34	$123.35	$123.30
Purchase #2	$165.29	13.199%	$187.1066	$187.11	$187.10	$187.10
Purchase #3	$118.74	13.163%	$134.3697	$134.37	$134.35	$134.40
Purchase #4	$105.92	7.766%	$114.1457	$114.15	$114.15	$114.10
Purchase #5	$111.60	4.570%	$116.7001	$116.70	$116.70	$116.70
Purchase #6	$112.77	6.609%	$120.223	$120.22	$120.20	$120.20
Purchase #7	$43.70	10.649%	$48.3536	$48.35	$48.35	$48.40
7 purchase totals =	$777.55		$844.2429	$844.24	$844.20	$844.20