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	$138.85	4.839%	$145.569	$145.57	$145.55	$145.60
Purchase #2	$32.51	5.419%	$34.2717	$34.27	$34.25	$34.30
Purchase #3	$70.74	10.821%	$78.3948	$78.39	$78.40	$78.40
Purchase #4	$76.33	8.749%	$83.0081	$83.01	$83.00	$83.00
Purchase #5	$114.68	3.837%	$119.0803	$119.08	$119.10	$119.10
Purchase #6	$144.44	13.746%	$164.2947	$164.29	$164.30	$164.30
Purchase #7	$123.98	7.852%	$133.7149	$133.71	$133.70	$133.70
7 purchase totals =	$701.53		$758.3335	$758.32	$758.30	$758.40