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	$178.32	10.367%	$196.8064	$196.81	$196.80	$196.80
Purchase #2	$72.59	3.615%	$75.2141	$75.21	$75.20	$75.20
Purchase #3	$249.40	9.642%	$273.4471	$273.45	$273.45	$273.40
Purchase #4	$90.87	9.619%	$99.6108	$99.61	$99.60	$99.60
Purchase #5	$232.77	9.674%	$255.2882	$255.29	$255.30	$255.30
Purchase #6	$21.93	11.203%	$24.3868	$24.39	$24.40	$24.40
Purchase #7	$120.50	9.699%	$132.1873	$132.19	$132.20	$132.20
7 purchase totals =	$966.38		$1,056.9407	$1,056.95	$1,056.95	$1,056.90