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	$213.85	13.461%	$242.6363	$242.64	$242.65	$242.60
Purchase #2	$104.64	12.514%	$117.7346	$117.73	$117.75	$117.70
Purchase #3	$106.89	5.325%	$112.5819	$112.58	$112.60	$112.60
Purchase #4	$93.69	7.508%	$100.7242	$100.72	$100.70	$100.70
Purchase #5	$126.89	3.441%	$131.2563	$131.26	$131.25	$131.30
Purchase #6	$246.87	11.109%	$274.2948	$274.29	$274.30	$274.30
Purchase #7	$154.85	13.381%	$175.5705	$175.57	$175.55	$175.60
7 purchase totals =	$1,047.68		$1,154.7986	$1,154.79	$1,154.80	$1,154.80