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	$68.83	4.840%	$72.1614	$72.16	$72.15	$72.20
Purchase #2	$189.36	12.246%	$212.549	$212.55	$212.55	$212.50
Purchase #3	$103.33	8.784%	$112.4065	$112.41	$112.40	$112.40
Purchase #4	$216.72	13.826%	$246.6837	$246.68	$246.70	$246.70
Purchase #5	$45.81	3.229%	$47.2892	$47.29	$47.30	$47.30
Purchase #6	$167.72	10.675%	$185.6241	$185.62	$185.60	$185.60
Purchase #7	$93.35	8.846%	$101.6077	$101.61	$101.60	$101.60
7 purchase totals =	$885.12		$978.3216	$978.32	$978.30	$978.30