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	$103.29	8.150%	$111.7081	$111.71	$111.70	$111.70
Purchase #2	$32.72	3.671%	$33.9212	$33.92	$33.90	$33.90
Purchase #3	$138.35	8.807%	$150.5345	$150.53	$150.55	$150.50
Purchase #4	$101.35	12.563%	$114.0826	$114.08	$114.10	$114.10
Purchase #5	$162.94	9.457%	$178.3492	$178.35	$178.35	$178.30
Purchase #6	$79.54	12.236%	$89.2725	$89.27	$89.25	$89.30
Purchase #7	$211.51	12.608%	$238.1772	$238.18	$238.20	$238.20
7 purchase totals =	$829.70		$916.0453	$916.04	$916.05	$916.00