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	$154.91	13.262%	$175.4542	$175.45	$175.45	$175.50
Purchase #2	$158.77	7.816%	$171.1795	$171.18	$171.20	$171.20
Purchase #3	$59.52	3.867%	$61.8216	$61.82	$61.80	$61.80
Purchase #4	$111.52	9.856%	$122.5114	$122.51	$122.50	$122.50
Purchase #5	$109.78	12.214%	$123.1885	$123.19	$123.20	$123.20
Purchase #6	$134.80	3.704%	$139.793	$139.79	$139.80	$139.80
Purchase #7	$215.99	5.791%	$228.498	$228.50	$228.50	$228.50
7 purchase totals =	$945.29		$1,022.4462	$1,022.44	$1,022.45	$1,022.50