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	$46.31	5.664%	$48.933	$48.93	$48.95	$48.90
Purchase #2	$63.94	4.303%	$66.6913	$66.69	$66.70	$66.70
Purchase #3	$160.53	12.688%	$180.898	$180.90	$180.90	$180.90
Purchase #4	$34.63	13.742%	$39.3889	$39.39	$39.40	$39.40
Purchase #5	$120.62	9.254%	$131.7822	$131.78	$131.80	$131.80
Purchase #6	$80.65	4.114%	$83.9679	$83.97	$83.95	$84.00
Purchase #7	$112.74	13.191%	$127.6115	$127.61	$127.60	$127.60
7 purchase totals =	$619.42		$679.2728	$679.27	$679.30	$679.30