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	$60.39	10.222%	$66.5631	$66.56	$66.55	$66.60
Purchase #2	$220.67	11.207%	$245.4005	$245.40	$245.40	$245.40
Purchase #3	$183.42	4.504%	$191.6812	$191.68	$191.70	$191.70
Purchase #4	$156.61	3.723%	$162.4406	$162.44	$162.45	$162.40
Purchase #5	$105.84	12.158%	$118.708	$118.71	$118.70	$118.70
Purchase #6	$25.55	8.190%	$27.6425	$27.64	$27.65	$27.60
Purchase #7	$199.52	11.504%	$222.4728	$222.47	$222.45	$222.50
7 purchase totals =	$952.00		$1,034.9087	$1,034.90	$1,034.90	$1,034.90