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	$140.27	5.834%	$148.4534	$148.45	$148.45	$148.50
Purchase #2	$53.42	11.119%	$59.3598	$59.36	$59.35	$59.40
Purchase #3	$90.42	11.608%	$100.916	$100.92	$100.90	$100.90
Purchase #4	$127.27	4.470%	$132.959	$132.96	$132.95	$133.00
Purchase #5	$101.47	7.358%	$108.9362	$108.94	$108.95	$108.90
Purchase #6	$66.83	13.344%	$75.7478	$75.75	$75.75	$75.70
Purchase #7	$227.88	12.669%	$256.7501	$256.75	$256.75	$256.80
7 purchase totals =	$807.56		$883.1223	$883.13	$883.10	$883.20