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	$47.43	6.119%	$50.3322	$50.33	$50.35	$50.30
Purchase #2	$165.32	9.212%	$180.5493	$180.55	$180.55	$180.50
Purchase #3	$205.57	6.679%	$219.3	$219.30	$219.30	$219.30
Purchase #4	$105.32	5.348%	$110.9525	$110.95	$110.95	$111.00
Purchase #5	$222.94	10.595%	$246.5605	$246.56	$246.55	$246.60
Purchase #6	$197.81	13.831%	$225.1691	$225.17	$225.15	$225.20
Purchase #7	$105.51	5.704%	$111.5283	$111.53	$111.55	$111.50
7 purchase totals =	$1,049.90		$1,144.3919	$1,144.39	$1,144.40	$1,144.40