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	$234.90	11.329%	$261.5118	$261.51	$261.50	$261.50
Purchase #2	$64.64	12.480%	$72.7071	$72.71	$72.70	$72.70
Purchase #3	$153.42	5.112%	$161.2628	$161.26	$161.25	$161.30
Purchase #4	$103.76	5.614%	$109.5851	$109.59	$109.60	$109.60
Purchase #5	$39.91	9.630%	$43.7533	$43.75	$43.75	$43.80
Purchase #6	$45.42	5.298%	$47.8264	$47.83	$47.85	$47.80
Purchase #7	$41.86	10.482%	$46.2478	$46.25	$46.25	$46.20
7 purchase totals =	$683.91		$742.8943	$742.90	$742.90	$742.90