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	$207.69	7.128%	$222.4941	$222.49	$222.50	$222.50
Purchase #2	$239.40	6.243%	$254.3457	$254.35	$254.35	$254.30
Purchase #3	$112.97	9.699%	$123.927	$123.93	$123.95	$123.90
Purchase #4	$197.97	6.452%	$210.743	$210.74	$210.75	$210.70
Purchase #5	$96.94	8.646%	$105.3214	$105.32	$105.30	$105.30
Purchase #6	$58.33	13.471%	$66.1876	$66.19	$66.20	$66.20
Purchase #7	$70.66	13.544%	$80.2302	$80.23	$80.25	$80.20
7 purchase totals =	$983.96		$1,063.2490	$1,063.25	$1,063.30	$1,063.10