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	$220.59	8.300%	$238.899	$238.90	$238.90	$238.90
Purchase #2	$130.62	11.395%	$145.5041	$145.50	$145.50	$145.50
Purchase #3	$32.86	4.546%	$34.3538	$34.35	$34.35	$34.40
Purchase #4	$249.72	7.649%	$268.8211	$268.82	$268.80	$268.80
Purchase #5	$188.62	11.681%	$210.6527	$210.65	$210.65	$210.70
Purchase #6	$54.50	5.870%	$57.6992	$57.70	$57.70	$57.70
Purchase #7	$123.32	12.387%	$138.5956	$138.60	$138.60	$138.60
7 purchase totals =	$1,000.23		$1,094.5255	$1,094.52	$1,094.50	$1,094.60