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	$107.47	3.783%	$111.5356	$111.54	$111.55	$111.50
Purchase #2	$231.89	9.833%	$254.6917	$254.69	$254.70	$254.70
Purchase #3	$90.39	4.821%	$94.7477	$94.75	$94.75	$94.70
Purchase #4	$74.40	11.832%	$83.203	$83.20	$83.20	$83.20
Purchase #5	$208.95	10.845%	$231.6106	$231.61	$231.60	$231.60
Purchase #6	$249.67	11.581%	$278.5843	$278.58	$278.60	$278.60
Purchase #7	$87.95	6.766%	$93.9007	$93.90	$93.90	$93.90
7 purchase totals =	$1,050.72		$1,148.2736	$1,148.27	$1,148.30	$1,148.20