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	$133.54	8.854%	$145.3636	$145.36	$145.35	$145.40
Purchase #2	$112.85	9.375%	$123.4297	$123.43	$123.45	$123.40
Purchase #3	$161.58	8.190%	$174.8134	$174.81	$174.80	$174.80
Purchase #4	$155.35	8.724%	$168.9027	$168.90	$168.90	$168.90
Purchase #5	$98.88	13.408%	$112.1378	$112.14	$112.15	$112.10
Purchase #6	$224.58	9.837%	$246.6719	$246.67	$246.65	$246.70
Purchase #7	$188.89	6.265%	$200.724	$200.72	$200.70	$200.70
7 purchase totals =	$1,075.67		$1,172.0431	$1,172.03	$1,172.00	$1,172.00