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	$216.71	9.859%	$238.0754	$238.08	$238.10	$238.10
Purchase #2	$241.30	8.810%	$262.5585	$262.56	$262.55	$262.60
Purchase #3	$91.83	8.783%	$99.8954	$99.90	$99.90	$99.90
Purchase #4	$176.32	13.365%	$199.8852	$199.89	$199.90	$199.90
Purchase #5	$48.60	6.674%	$51.8436	$51.84	$51.85	$51.80
Purchase #6	$40.63	9.350%	$44.4289	$44.43	$44.45	$44.40
Purchase #7	$87.71	3.672%	$90.9307	$90.93	$90.95	$90.90
7 purchase totals =	$903.10		$987.6177	$987.63	$987.70	$987.60