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	$128.50	6.192%	$136.4567	$136.46	$136.45	$136.50
Purchase #2	$194.80	9.551%	$213.4053	$213.41	$213.40	$213.40
Purchase #3	$58.31	6.683%	$62.2069	$62.21	$62.20	$62.20
Purchase #4	$243.76	4.541%	$254.8291	$254.83	$254.85	$254.80
Purchase #5	$83.28	8.774%	$90.587	$90.59	$90.60	$90.60
Purchase #6	$38.85	13.178%	$43.9697	$43.97	$43.95	$44.00
Purchase #7	$80.51	6.791%	$85.9774	$85.98	$86.00	$86.00
7 purchase totals =	$828.01		$887.4321	$887.45	$887.45	$887.50