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	$180.86	4.199%	$188.4543	$188.45	$188.45	$188.50
Purchase #2	$142.48	11.301%	$158.5817	$158.58	$158.60	$158.60
Purchase #3	$126.30	11.311%	$140.5858	$140.59	$140.60	$140.60
Purchase #4	$201.26	4.500%	$210.3167	$210.32	$210.30	$210.30
Purchase #5	$244.61	5.820%	$258.8463	$258.85	$258.85	$258.80
Purchase #6	$198.89	13.656%	$226.0504	$226.05	$226.05	$226.10
Purchase #7	$92.93	11.257%	$103.3911	$103.39	$103.40	$103.40
7 purchase totals =	$1,187.33		$1,286.2263	$1,286.23	$1,286.25	$1,286.30