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	$99.55	4.307%	$103.8376	$103.84	$103.85	$103.80
Purchase #2	$216.96	12.135%	$243.2881	$243.29	$243.30	$243.30
Purchase #3	$100.92	3.776%	$104.7307	$104.73	$104.75	$104.70
Purchase #4	$144.82	5.586%	$152.9096	$152.91	$152.90	$152.90
Purchase #5	$97.29	6.470%	$103.5847	$103.58	$103.60	$103.60
Purchase #6	$134.27	4.549%	$140.3779	$140.38	$140.40	$140.40
Purchase #7	$178.95	8.720%	$194.5544	$194.55	$194.55	$194.60
7 purchase totals =	$972.76		$1,043.2830	$1,043.28	$1,043.35	$1,043.30