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	$206.61	9.567%	$226.3764	$226.38	$226.40	$226.40
Purchase #2	$238.85	7.574%	$256.9405	$256.94	$256.95	$256.90
Purchase #3	$104.75	3.667%	$108.5912	$108.59	$108.60	$108.60
Purchase #4	$158.98	6.530%	$169.3614	$169.36	$169.35	$169.40
Purchase #5	$41.91	11.851%	$46.8768	$46.88	$46.90	$46.90
Purchase #6	$10.93	13.475%	$12.4028	$12.40	$12.40	$12.40
Purchase #7	$138.40	4.600%	$144.7664	$144.77	$144.75	$144.80
7 purchase totals =	$900.43		$965.3155	$965.32	$965.35	$965.40