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	$229.77	13.655%	$261.1451	$261.15	$261.15	$261.10
Purchase #2	$208.46	3.335%	$215.4121	$215.41	$215.40	$215.40
Purchase #3	$100.80	7.130%	$107.987	$107.99	$108.00	$108.00
Purchase #4	$99.43	4.105%	$103.5116	$103.51	$103.50	$103.50
Purchase #5	$174.95	13.834%	$199.1526	$199.15	$199.15	$199.20
Purchase #6	$88.87	3.790%	$92.2382	$92.24	$92.25	$92.20
Purchase #7	$130.48	10.484%	$144.1595	$144.16	$144.15	$144.20
7 purchase totals =	$1,032.76		$1,123.6061	$1,123.61	$1,123.60	$1,123.60