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	$165.78	10.572%	$183.3063	$183.31	$183.30	$183.30
Purchase #2	$49.77	13.746%	$56.6114	$56.61	$56.60	$56.60
Purchase #3	$91.32	13.743%	$103.8701	$103.87	$103.85	$103.90
Purchase #4	$13.31	10.447%	$14.7005	$14.70	$14.70	$14.70
Purchase #5	$196.62	8.487%	$213.3071	$213.31	$213.30	$213.30
Purchase #6	$200.48	5.152%	$210.8087	$210.81	$210.80	$210.80
Purchase #7	$227.96	5.470%	$240.4294	$240.43	$240.45	$240.40
7 purchase totals =	$945.24		$1,023.0335	$1,023.04	$1,023.00	$1,023.00