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	$138.63	10.264%	$152.859	$152.86	$152.85	$152.90
Purchase #2	$70.47	11.793%	$78.7805	$78.78	$78.80	$78.80
Purchase #3	$238.89	11.753%	$266.9667	$266.97	$266.95	$267.00
Purchase #4	$186.91	13.113%	$211.4195	$211.42	$211.40	$211.40
Purchase #5	$196.45	8.530%	$213.2072	$213.21	$213.20	$213.20
Purchase #6	$128.75	9.147%	$140.5268	$140.53	$140.55	$140.50
Purchase #7	$56.43	8.767%	$61.3772	$61.38	$61.40	$61.40
7 purchase totals =	$1,016.53		$1,125.1369	$1,125.15	$1,125.15	$1,125.20