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	$210.85	5.296%	$222.0166	$222.02	$222.00	$222.00
Purchase #2	$243.75	4.835%	$255.5353	$255.54	$255.55	$255.50
Purchase #3	$81.66	10.735%	$90.4262	$90.43	$90.45	$90.40
Purchase #4	$50.73	3.849%	$52.6826	$52.68	$52.70	$52.70
Purchase #5	$60.79	6.147%	$64.5268	$64.53	$64.55	$64.50
Purchase #6	$8.67	12.681%	$9.7694	$9.77	$9.75	$9.80
Purchase #7	$65.77	9.422%	$71.9668	$71.97	$71.95	$72.00
7 purchase totals =	$722.22		$766.9237	$766.94	$766.95	$766.90