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	$100.83	3.431%	$104.2895	$104.29	$104.30	$104.30
Purchase #2	$194.91	9.160%	$212.7638	$212.76	$212.75	$212.80
Purchase #3	$92.35	11.569%	$103.034	$103.03	$103.05	$103.00
Purchase #4	$90.83	13.292%	$102.9031	$102.90	$102.90	$102.90
Purchase #5	$184.36	12.574%	$207.5414	$207.54	$207.55	$207.50
Purchase #6	$206.90	7.729%	$222.8913	$222.89	$222.90	$222.90
Purchase #7	$153.94	4.849%	$161.4046	$161.40	$161.40	$161.40
7 purchase totals =	$1,024.12		$1,114.8277	$1,114.81	$1,114.85	$1,114.80