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	$167.88	10.560%	$185.6081	$185.61	$185.60	$185.60
Purchase #2	$56.61	4.300%	$59.0442	$59.04	$59.05	$59.00
Purchase #3	$43.96	13.262%	$49.79	$49.79	$49.80	$49.80
Purchase #4	$158.45	5.673%	$167.4389	$167.44	$167.45	$167.40
Purchase #5	$137.45	9.507%	$150.5174	$150.52	$150.50	$150.50
Purchase #6	$22.28	11.226%	$24.7812	$24.78	$24.80	$24.80
Purchase #7	$240.95	5.567%	$254.3637	$254.36	$254.35	$254.40
7 purchase totals =	$827.58		$891.5435	$891.54	$891.55	$891.50