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	$160.74	11.566%	$179.3312	$179.33	$179.35	$179.30
Purchase #2	$60.67	10.379%	$66.9669	$66.97	$66.95	$67.00
Purchase #3	$90.42	11.509%	$100.8264	$100.83	$100.85	$100.80
Purchase #4	$142.84	11.288%	$158.9638	$158.96	$158.95	$159.00
Purchase #5	$42.95	5.864%	$45.4686	$45.47	$45.45	$45.50
Purchase #6	$248.93	5.197%	$261.8669	$261.87	$261.85	$261.90
Purchase #7	$210.85	5.465%	$222.373	$222.37	$222.35	$222.40
7 purchase totals =	$957.40		$1,035.7968	$1,035.80	$1,035.75	$1,035.90