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	$140.94	10.408%	$155.609	$155.61	$155.60	$155.60
Purchase #2	$80.63	10.816%	$89.3509	$89.35	$89.35	$89.40
Purchase #3	$69.43	8.565%	$75.3767	$75.38	$75.40	$75.40
Purchase #4	$148.61	7.783%	$160.1763	$160.18	$160.20	$160.20
Purchase #5	$56.85	11.702%	$63.5026	$63.50	$63.50	$63.50
Purchase #6	$142.59	9.857%	$156.6451	$156.65	$156.65	$156.60
Purchase #7	$248.38	5.571%	$262.2172	$262.22	$262.20	$262.20
7 purchase totals =	$887.43		$962.8778	$962.89	$962.90	$962.90