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	$116.99	5.503%	$123.428	$123.43	$123.45	$123.40
Purchase #2	$234.95	4.636%	$245.8423	$245.84	$245.85	$245.80
Purchase #3	$19.26	11.825%	$21.5375	$21.54	$21.55	$21.50
Purchase #4	$126.25	13.584%	$143.3998	$143.40	$143.40	$143.40
Purchase #5	$75.39	5.510%	$79.544	$79.54	$79.55	$79.50
Purchase #6	$104.29	7.753%	$112.3756	$112.38	$112.40	$112.40
Purchase #7	$216.88	10.142%	$238.876	$238.88	$238.90	$238.90
7 purchase totals =	$894.01		$965.0032	$965.01	$965.10	$964.90