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	$196.42	9.822%	$215.7124	$215.71	$215.70	$215.70
Purchase #2	$62.56	5.863%	$66.2279	$66.23	$66.25	$66.20
Purchase #3	$178.49	10.846%	$197.849	$197.85	$197.85	$197.80
Purchase #4	$213.66	10.273%	$235.6093	$235.61	$235.60	$235.60
Purchase #5	$62.79	7.460%	$67.4741	$67.47	$67.45	$67.50
Purchase #6	$105.48	10.553%	$116.6113	$116.61	$116.60	$116.60
Purchase #7	$223.58	9.609%	$245.0638	$245.06	$245.05	$245.10
7 purchase totals =	$1,042.98		$1,144.5478	$1,144.54	$1,144.50	$1,144.50