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	$192.65	10.415%	$212.7145	$212.71	$212.70	$212.70
Purchase #2	$78.68	6.678%	$83.9343	$83.93	$83.95	$83.90
Purchase #3	$132.78	8.364%	$143.8857	$143.89	$143.90	$143.90
Purchase #4	$222.65	10.466%	$245.9525	$245.95	$245.95	$246.00
Purchase #5	$152.39	10.641%	$168.6058	$168.61	$168.60	$168.60
Purchase #6	$224.41	3.208%	$231.6091	$231.61	$231.60	$231.60
Purchase #7	$128.90	10.631%	$142.6034	$142.60	$142.60	$142.60
7 purchase totals =	$1,132.46		$1,229.3053	$1,229.30	$1,229.30	$1,229.30