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	$61.79	4.533%	$64.5909	$64.59	$64.60	$64.60
Purchase #2	$46.25	5.103%	$48.6101	$48.61	$48.60	$48.60
Purchase #3	$203.91	9.208%	$222.686	$222.69	$222.70	$222.70
Purchase #4	$25.56	6.832%	$27.3063	$27.31	$27.30	$27.30
Purchase #5	$58.75	12.178%	$65.9046	$65.90	$65.90	$65.90
Purchase #6	$123.47	7.455%	$132.6747	$132.67	$132.65	$132.70
Purchase #7	$54.95	4.748%	$57.559	$57.56	$57.55	$57.60
7 purchase totals =	$574.68		$619.3316	$619.33	$619.30	$619.40