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	$211.64	10.700%	$234.2855	$234.29	$234.30	$234.30
Purchase #2	$250.71	9.536%	$274.6177	$274.62	$274.60	$274.60
Purchase #3	$218.63	3.417%	$226.1006	$226.10	$226.10	$226.10
Purchase #4	$20.65	4.452%	$21.5693	$21.57	$21.55	$21.60
Purchase #5	$38.96	11.369%	$43.3894	$43.39	$43.40	$43.40
Purchase #6	$182.97	4.304%	$190.845	$190.85	$190.85	$190.80
Purchase #7	$109.60	10.204%	$120.7836	$120.78	$120.80	$120.80
7 purchase totals =	$1,033.16		$1,111.5911	$1,111.60	$1,111.60	$1,111.60