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	$105.41	13.379%	$119.5128	$119.51	$119.50	$119.50
Purchase #2	$58.82	10.262%	$64.8561	$64.86	$64.85	$64.90
Purchase #3	$31.64	3.387%	$32.7116	$32.71	$32.70	$32.70
Purchase #4	$14.60	11.445%	$16.271	$16.27	$16.25	$16.30
Purchase #5	$38.73	10.828%	$42.9237	$42.92	$42.90	$42.90
Purchase #6	$126.50	3.261%	$130.6252	$130.63	$130.65	$130.60
Purchase #7	$78.66	9.133%	$85.844	$85.84	$85.85	$85.80
7 purchase totals =	$454.36		$492.7444	$492.74	$492.70	$492.70