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	$98.32	5.274%	$103.5054	$103.51	$103.50	$103.50
Purchase #2	$12.49	5.665%	$13.1976	$13.20	$13.20	$13.20
Purchase #3	$16.93	8.555%	$18.3784	$18.38	$18.40	$18.40
Purchase #4	$131.47	8.109%	$142.1309	$142.13	$142.15	$142.10
Purchase #5	$138.60	6.596%	$147.7421	$147.74	$147.75	$147.70
Purchase #6	$40.68	12.680%	$45.8382	$45.84	$45.85	$45.80
Purchase #7	$150.75	3.166%	$155.5227	$155.52	$155.50	$155.50
7 purchase totals =	$589.24		$626.3153	$626.32	$626.35	$626.20