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	$188.29	9.142%	$205.5035	$205.50	$205.50	$205.50
Purchase #2	$165.74	3.786%	$172.0149	$172.01	$172.00	$172.00
Purchase #3	$250.94	4.243%	$261.5874	$261.59	$261.60	$261.60
Purchase #4	$151.34	9.349%	$165.4888	$165.49	$165.50	$165.50
Purchase #5	$96.27	13.301%	$109.0749	$109.07	$109.05	$109.10
Purchase #6	$31.78	13.580%	$36.0957	$36.10	$36.10	$36.10
Purchase #7	$23.87	11.785%	$26.6831	$26.68	$26.70	$26.70
7 purchase totals =	$908.23		$976.4483	$976.44	$976.45	$976.50