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	$75.74	3.812%	$78.6272	$78.63	$78.65	$78.60
Purchase #2	$172.94	11.174%	$192.2643	$192.26	$192.25	$192.30
Purchase #3	$15.47	6.360%	$16.4539	$16.45	$16.45	$16.50
Purchase #4	$127.77	3.716%	$132.5179	$132.52	$132.50	$132.50
Purchase #5	$221.94	7.397%	$238.3569	$238.36	$238.35	$238.40
Purchase #6	$62.66	7.514%	$67.3683	$67.37	$67.35	$67.40
Purchase #7	$37.78	10.385%	$41.7035	$41.70	$41.70	$41.70
7 purchase totals =	$714.30		$767.2920	$767.29	$767.25	$767.40