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	$78.81	13.750%	$89.6464	$89.65	$89.65	$89.60
Purchase #2	$56.42	11.427%	$62.8671	$62.87	$62.85	$62.90
Purchase #3	$19.88	10.123%	$21.8925	$21.89	$21.90	$21.90
Purchase #4	$24.46	3.779%	$25.3843	$25.38	$25.40	$25.40
Purchase #5	$164.71	6.752%	$175.8312	$175.83	$175.85	$175.80
Purchase #6	$141.88	5.655%	$149.9033	$149.90	$149.90	$149.90
Purchase #7	$69.31	12.434%	$77.928	$77.93	$77.95	$77.90
7 purchase totals =	$555.47		$603.4528	$603.45	$603.50	$603.40