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	$116.33	10.519%	$128.5668	$128.57	$128.55	$128.60
Purchase #2	$235.89	5.721%	$249.3853	$249.39	$249.40	$249.40
Purchase #3	$215.28	12.668%	$242.5517	$242.55	$242.55	$242.60
Purchase #4	$24.95	9.458%	$27.3098	$27.31	$27.30	$27.30
Purchase #5	$14.65	8.748%	$15.9316	$15.93	$15.95	$15.90
Purchase #6	$84.42	6.125%	$89.5907	$89.59	$89.60	$89.60
Purchase #7	$99.37	13.275%	$112.5614	$112.56	$112.55	$112.60
7 purchase totals =	$790.89		$865.8973	$865.90	$865.90	$866.00