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	$166.81	7.197%	$178.8153	$178.82	$178.80	$178.80
Purchase #2	$63.26	3.124%	$65.2362	$65.24	$65.25	$65.20
Purchase #3	$127.56	3.541%	$132.0769	$132.08	$132.10	$132.10
Purchase #4	$76.69	6.751%	$81.8673	$81.87	$81.85	$81.90
Purchase #5	$20.73	3.404%	$21.4356	$21.44	$21.45	$21.40
Purchase #6	$30.83	6.341%	$32.7849	$32.78	$32.80	$32.80
Purchase #7	$12.34	12.284%	$13.8558	$13.86	$13.85	$13.90
7 purchase totals =	$498.22		$526.0720	$526.09	$526.10	$526.10