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	$194.96	12.526%	$219.3807	$219.38	$219.40	$219.40
Purchase #2	$93.92	10.445%	$103.7299	$103.73	$103.75	$103.70
Purchase #3	$38.37	10.763%	$42.4998	$42.50	$42.50	$42.50
Purchase #4	$247.27	11.792%	$276.4281	$276.43	$276.45	$276.40
Purchase #5	$219.30	7.786%	$236.3747	$236.37	$236.35	$236.40
Purchase #6	$146.96	6.641%	$156.7196	$156.72	$156.70	$156.70
Purchase #7	$43.52	12.820%	$49.0993	$49.10	$49.10	$49.10
7 purchase totals =	$984.30		$1,084.2321	$1,084.23	$1,084.25	$1,084.20