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	$39.39	9.542%	$43.1486	$43.15	$43.15	$43.10
Purchase #2	$11.76	6.378%	$12.5101	$12.51	$12.50	$12.50
Purchase #3	$36.76	12.817%	$41.4715	$41.47	$41.45	$41.50
Purchase #4	$74.94	8.646%	$81.4193	$81.42	$81.40	$81.40
Purchase #5	$78.66	13.527%	$89.3003	$89.30	$89.30	$89.30
Purchase #6	$156.52	4.428%	$163.4507	$163.45	$163.45	$163.50
Purchase #7	$209.54	6.192%	$222.5147	$222.51	$222.50	$222.50
7 purchase totals =	$607.57		$653.8152	$653.81	$653.75	$653.80