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	$51.30	6.131%	$54.4452	$54.45	$54.45	$54.40
Purchase #2	$178.69	5.632%	$188.7538	$188.75	$188.75	$188.80
Purchase #3	$221.52	5.846%	$234.4701	$234.47	$234.45	$234.50
Purchase #4	$172.58	3.391%	$178.4322	$178.43	$178.45	$178.40
Purchase #5	$200.77	12.525%	$225.9164	$225.92	$225.90	$225.90
Purchase #6	$146.28	10.304%	$161.3527	$161.35	$161.35	$161.40
Purchase #7	$27.45	13.674%	$31.2035	$31.20	$31.20	$31.20
7 purchase totals =	$998.59		$1,074.5739	$1,074.57	$1,074.55	$1,074.60