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	$180.38	8.256%	$195.2722	$195.27	$195.25	$195.30
Purchase #2	$78.77	12.711%	$88.7825	$88.78	$88.80	$88.80
Purchase #3	$34.79	7.589%	$37.4302	$37.43	$37.45	$37.40
Purchase #4	$91.90	9.443%	$100.5781	$100.58	$100.60	$100.60
Purchase #5	$202.34	5.308%	$213.0802	$213.08	$213.10	$213.10
Purchase #6	$72.49	11.274%	$80.6625	$80.66	$80.65	$80.70
Purchase #7	$20.49	8.256%	$22.1817	$22.18	$22.20	$22.20
7 purchase totals =	$681.16		$737.9874	$737.98	$738.05	$738.10