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	$85.42	12.218%	$95.8566	$95.86	$95.85	$95.90
Purchase #2	$236.62	9.295%	$258.6138	$258.61	$258.60	$258.60
Purchase #3	$231.94	11.244%	$258.0193	$258.02	$258.00	$258.00
Purchase #4	$63.39	7.719%	$68.2831	$68.28	$68.30	$68.30
Purchase #5	$78.66	13.579%	$89.3412	$89.34	$89.35	$89.30
Purchase #6	$235.48	12.628%	$265.2164	$265.22	$265.20	$265.20
Purchase #7	$10.57	7.688%	$11.3826	$11.38	$11.40	$11.40
7 purchase totals =	$942.08		$1,046.7130	$1,046.71	$1,046.70	$1,046.70