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	$92.45	11.453%	$103.0383	$103.04	$103.05	$103.00
Purchase #2	$11.44	13.438%	$12.9773	$12.98	$13.00	$13.00
Purchase #3	$11.93	13.562%	$13.5479	$13.55	$13.55	$13.50
Purchase #4	$21.73	13.167%	$24.5912	$24.59	$24.60	$24.60
Purchase #5	$48.40	10.734%	$53.5953	$53.60	$53.60	$53.60
Purchase #6	$129.94	8.850%	$141.4397	$141.44	$141.45	$141.40
Purchase #7	$47.66	10.246%	$52.5432	$52.54	$52.55	$52.50
7 purchase totals =	$363.55		$401.7329	$401.74	$401.80	$401.60