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	$130.25	11.503%	$145.2327	$145.23	$145.25	$145.20
Purchase #2	$238.40	7.516%	$256.3181	$256.32	$256.30	$256.30
Purchase #3	$200.35	6.429%	$213.2305	$213.23	$213.25	$213.20
Purchase #4	$97.32	6.214%	$103.3675	$103.37	$103.35	$103.40
Purchase #5	$71.55	12.545%	$80.5259	$80.53	$80.55	$80.50
Purchase #6	$128.76	10.260%	$141.9708	$141.97	$141.95	$142.00
Purchase #7	$124.86	11.281%	$138.9455	$138.95	$138.95	$138.90
7 purchase totals =	$991.49		$1,079.5910	$1,079.60	$1,079.60	$1,079.50