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	$72.32	8.653%	$78.5778	$78.58	$78.60	$78.60
Purchase #2	$18.94	9.564%	$20.7514	$20.75	$20.75	$20.80
Purchase #3	$154.30	4.325%	$160.9735	$160.97	$160.95	$161.00
Purchase #4	$240.81	9.336%	$263.292	$263.29	$263.30	$263.30
Purchase #5	$246.51	13.745%	$280.3928	$280.39	$280.40	$280.40
Purchase #6	$75.79	7.490%	$81.4667	$81.47	$81.45	$81.50
Purchase #7	$234.74	9.223%	$256.3901	$256.39	$256.40	$256.40
7 purchase totals =	$1,043.41		$1,141.8443	$1,141.84	$1,141.85	$1,142.00