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	$125.51	13.339%	$142.2518	$142.25	$142.25	$142.30
Purchase #2	$90.25	13.305%	$102.2578	$102.26	$102.25	$102.30
Purchase #3	$78.73	5.145%	$82.7807	$82.78	$82.80	$82.80
Purchase #4	$43.45	13.513%	$49.3214	$49.32	$49.30	$49.30
Purchase #5	$91.53	9.513%	$100.2372	$100.24	$100.25	$100.20
Purchase #6	$16.75	7.496%	$18.0056	$18.01	$18.00	$18.00
Purchase #7	$233.81	13.177%	$264.6191	$264.62	$264.60	$264.60
7 purchase totals =	$680.03		$759.4736	$759.48	$759.45	$759.50