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	$95.88	10.820%	$106.2542	$106.25	$106.25	$106.30
Purchase #2	$155.29	13.219%	$175.8178	$175.82	$175.80	$175.80
Purchase #3	$80.60	6.174%	$85.5762	$85.58	$85.60	$85.60
Purchase #4	$10.45	11.866%	$11.69	$11.69	$11.70	$11.70
Purchase #5	$177.91	11.601%	$198.5493	$198.55	$198.55	$198.50
Purchase #6	$31.55	13.363%	$35.766	$35.77	$35.75	$35.80
Purchase #7	$226.83	12.586%	$255.3788	$255.38	$255.40	$255.40
7 purchase totals =	$778.51		$869.0323	$869.04	$869.05	$869.10