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	$148.78	12.460%	$167.318	$167.32	$167.30	$167.30
Purchase #2	$141.25	9.243%	$154.3057	$154.31	$154.30	$154.30
Purchase #3	$85.72	10.373%	$94.6117	$94.61	$94.60	$94.60
Purchase #4	$63.78	3.636%	$66.099	$66.10	$66.10	$66.10
Purchase #5	$168.73	3.443%	$174.5394	$174.54	$174.55	$174.50
Purchase #6	$28.80	3.653%	$29.8521	$29.85	$29.85	$29.90
Purchase #7	$43.91	10.355%	$48.4569	$48.46	$48.45	$48.50
7 purchase totals =	$680.97		$735.1828	$735.19	$735.15	$735.20