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	$231.27	8.738%	$251.4784	$251.48	$251.50	$251.50
Purchase #2	$119.68	10.210%	$131.8993	$131.90	$131.90	$131.90
Purchase #3	$14.87	4.738%	$15.5745	$15.57	$15.55	$15.60
Purchase #4	$88.48	13.811%	$100.7	$100.70	$100.70	$100.70
Purchase #5	$56.55	9.311%	$61.8154	$61.82	$61.80	$61.80
Purchase #6	$242.48	7.480%	$260.6175	$260.62	$260.60	$260.60
Purchase #7	$115.28	10.663%	$127.5723	$127.57	$127.55	$127.60
7 purchase totals =	$868.61		$949.6574	$949.66	$949.60	$949.70