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	$215.82	11.822%	$241.3342	$241.33	$241.35	$241.30
Purchase #2	$28.56	11.850%	$31.9444	$31.94	$31.95	$31.90
Purchase #3	$49.59	10.379%	$54.7369	$54.74	$54.75	$54.70
Purchase #4	$148.94	12.464%	$167.5039	$167.50	$167.50	$167.50
Purchase #5	$93.89	8.286%	$101.6697	$101.67	$101.65	$101.70
Purchase #6	$70.65	9.260%	$77.1922	$77.19	$77.20	$77.20
Purchase #7	$62.93	4.265%	$65.614	$65.61	$65.60	$65.60
7 purchase totals =	$670.38		$739.9953	$739.98	$740.00	$739.90