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	$46.60	4.500%	$48.697	$48.70	$48.70	$48.70
Purchase #2	$182.94	13.232%	$207.1466	$207.15	$207.15	$207.10
Purchase #3	$50.95	12.855%	$57.4996	$57.50	$57.50	$57.50
Purchase #4	$41.67	11.305%	$46.3808	$46.38	$46.40	$46.40
Purchase #5	$125.71	11.726%	$140.4508	$140.45	$140.45	$140.50
Purchase #6	$171.42	13.672%	$194.8565	$194.86	$194.85	$194.90
Purchase #7	$188.95	4.182%	$196.8519	$196.85	$196.85	$196.90
7 purchase totals =	$808.24		$891.8832	$891.89	$891.90	$892.00