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	$221.29	9.161%	$241.5624	$241.56	$241.55	$241.60
Purchase #2	$179.47	5.822%	$189.9187	$189.92	$189.90	$189.90
Purchase #3	$155.71	5.139%	$163.7119	$163.71	$163.70	$163.70
Purchase #4	$42.72	10.230%	$47.0903	$47.09	$47.10	$47.10
Purchase #5	$37.65	13.155%	$42.6029	$42.60	$42.60	$42.60
Purchase #6	$159.31	5.657%	$168.3222	$168.32	$168.30	$168.30
Purchase #7	$179.58	6.691%	$191.5957	$191.60	$191.60	$191.60
7 purchase totals =	$975.73		$1,044.8041	$1,044.80	$1,044.75	$1,044.80