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	$109.38	7.679%	$117.7793	$117.78	$117.80	$117.80
Purchase #2	$87.70	3.496%	$90.766	$90.77	$90.75	$90.80
Purchase #3	$203.81	5.774%	$215.578	$215.58	$215.60	$215.60
Purchase #4	$17.85	10.256%	$19.6807	$19.68	$19.70	$19.70
Purchase #5	$58.46	5.648%	$61.7618	$61.76	$61.75	$61.80
Purchase #6	$38.82	12.299%	$43.5945	$43.59	$43.60	$43.60
Purchase #7	$156.58	5.731%	$165.5536	$165.55	$165.55	$165.60
7 purchase totals =	$672.60		$714.7139	$714.71	$714.75	$714.90