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	$95.47	5.637%	$100.8516	$100.85	$100.85	$100.90
Purchase #2	$102.88	11.394%	$114.6021	$114.60	$114.60	$114.60
Purchase #3	$63.25	13.358%	$71.6989	$71.70	$71.70	$71.70
Purchase #4	$54.50	9.392%	$59.6186	$59.62	$59.60	$59.60
Purchase #5	$118.53	7.363%	$127.2574	$127.26	$127.25	$127.30
Purchase #6	$196.37	8.553%	$213.1655	$213.17	$213.15	$213.20
Purchase #7	$208.32	9.644%	$228.4104	$228.41	$228.40	$228.40
7 purchase totals =	$839.32		$915.6045	$915.61	$915.55	$915.70