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	$133.54	5.637%	$141.0676	$141.07	$141.05	$141.10
Purchase #2	$185.31	8.243%	$200.5851	$200.59	$200.60	$200.60
Purchase #3	$69.61	9.742%	$76.3914	$76.39	$76.40	$76.40
Purchase #4	$244.43	5.874%	$258.7878	$258.79	$258.80	$258.80
Purchase #5	$23.99	12.804%	$27.0617	$27.06	$27.05	$27.10
Purchase #6	$78.77	13.630%	$89.5064	$89.51	$89.50	$89.50
Purchase #7	$156.45	10.696%	$173.1839	$173.18	$173.20	$173.20
7 purchase totals =	$892.10		$966.5839	$966.59	$966.60	$966.70