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	$167.47	4.708%	$175.3545	$175.35	$175.35	$175.40
Purchase #2	$14.28	5.469%	$15.061	$15.06	$15.05	$15.10
Purchase #3	$19.86	3.653%	$20.5855	$20.59	$20.60	$20.60
Purchase #4	$109.86	13.639%	$124.8438	$124.84	$124.85	$124.80
Purchase #5	$11.85	8.143%	$12.8149	$12.81	$12.80	$12.80
Purchase #6	$68.30	7.213%	$73.2265	$73.23	$73.25	$73.20
Purchase #7	$223.54	9.856%	$245.5721	$245.57	$245.55	$245.60
7 purchase totals =	$615.16		$667.4583	$667.45	$667.45	$667.50