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	$179.64	9.378%	$196.4866	$196.49	$196.50	$196.50
Purchase #2	$88.41	13.160%	$100.0448	$100.04	$100.05	$100.00
Purchase #3	$121.97	13.485%	$138.4177	$138.42	$138.40	$138.40
Purchase #4	$19.92	6.373%	$21.1895	$21.19	$21.20	$21.20
Purchase #5	$63.78	8.603%	$69.267	$69.27	$69.25	$69.30
Purchase #6	$15.80	13.502%	$17.9333	$17.93	$17.95	$17.90
Purchase #7	$174.91	5.706%	$184.8904	$184.89	$184.90	$184.90
7 purchase totals =	$664.43		$728.2293	$728.23	$728.25	$728.20