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	$171.88	8.441%	$186.3884	$186.39	$186.40	$186.40
Purchase #2	$188.75	8.837%	$205.4298	$205.43	$205.45	$205.40
Purchase #3	$43.32	5.247%	$45.593	$45.59	$45.60	$45.60
Purchase #4	$42.50	13.224%	$48.1202	$48.12	$48.10	$48.10
Purchase #5	$224.47	3.108%	$231.4465	$231.45	$231.45	$231.40
Purchase #6	$205.90	4.469%	$215.1017	$215.10	$215.10	$215.10
Purchase #7	$28.92	9.849%	$31.7683	$31.77	$31.75	$31.80
7 purchase totals =	$905.74		$963.8479	$963.85	$963.85	$963.80