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	$165.32	8.467%	$179.3176	$179.32	$179.30	$179.30
Purchase #2	$20.60	6.336%	$21.9052	$21.91	$21.90	$21.90
Purchase #3	$127.97	8.673%	$139.0688	$139.07	$139.05	$139.10
Purchase #4	$98.25	5.338%	$103.4946	$103.49	$103.50	$103.50
Purchase #5	$191.89	9.715%	$210.5321	$210.53	$210.55	$210.50
Purchase #6	$94.89	4.378%	$99.0443	$99.04	$99.05	$99.00
Purchase #7	$183.39	4.739%	$192.0809	$192.08	$192.10	$192.10
7 purchase totals =	$882.31		$945.4435	$945.44	$945.45	$945.40