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	$40.25	12.709%	$45.3654	$45.37	$45.35	$45.40
Purchase #2	$145.64	13.579%	$165.4165	$165.42	$165.40	$165.40
Purchase #3	$222.40	8.383%	$241.0438	$241.04	$241.05	$241.00
Purchase #4	$225.50	6.688%	$240.5814	$240.58	$240.60	$240.60
Purchase #5	$73.88	10.404%	$81.5665	$81.57	$81.55	$81.60
Purchase #6	$86.98	9.785%	$95.491	$95.49	$95.50	$95.50
Purchase #7	$224.45	7.767%	$241.883	$241.88	$241.90	$241.90
7 purchase totals =	$1,019.10		$1,111.3476	$1,111.35	$1,111.35	$1,111.40