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	$112.25	10.333%	$123.8488	$123.85	$123.85	$123.80
Purchase #2	$68.25	6.403%	$72.62	$72.62	$72.60	$72.60
Purchase #3	$70.46	9.802%	$77.3665	$77.37	$77.35	$77.40
Purchase #4	$119.48	12.412%	$134.3099	$134.31	$134.30	$134.30
Purchase #5	$18.64	13.521%	$21.1603	$21.16	$21.15	$21.20
Purchase #6	$238.28	8.832%	$259.3249	$259.32	$259.30	$259.30
Purchase #7	$117.81	11.869%	$131.7929	$131.79	$131.80	$131.80
7 purchase totals =	$745.17		$820.4233	$820.42	$820.35	$820.40