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	$38.52	13.863%	$43.86	$43.86	$43.85	$43.90
Purchase #2	$39.96	9.508%	$43.7594	$43.76	$43.75	$43.80
Purchase #3	$67.49	13.380%	$76.5202	$76.52	$76.50	$76.50
Purchase #4	$238.91	9.695%	$262.0723	$262.07	$262.05	$262.10
Purchase #5	$10.61	9.532%	$11.6213	$11.62	$11.60	$11.60
Purchase #6	$29.39	11.872%	$32.8792	$32.88	$32.90	$32.90
Purchase #7	$77.74	8.723%	$84.5213	$84.52	$84.50	$84.50
7 purchase totals =	$502.62		$555.2337	$555.23	$555.15	$555.30