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	$77.45	7.859%	$83.5368	$83.54	$83.55	$83.50
Purchase #2	$118.84	9.660%	$130.3199	$130.32	$130.30	$130.30
Purchase #3	$182.51	7.864%	$196.8626	$196.86	$196.85	$196.90
Purchase #4	$63.81	5.675%	$67.4312	$67.43	$67.45	$67.40
Purchase #5	$224.30	6.772%	$239.4896	$239.49	$239.50	$239.50
Purchase #6	$229.64	3.475%	$237.62	$237.62	$237.60	$237.60
Purchase #7	$83.98	11.597%	$93.7192	$93.72	$93.70	$93.70
7 purchase totals =	$980.53		$1,048.9793	$1,048.98	$1,048.95	$1,048.90