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	$141.77	10.620%	$156.826	$156.83	$156.85	$156.80
Purchase #2	$111.92	4.634%	$117.1064	$117.11	$117.10	$117.10
Purchase #3	$179.48	7.208%	$192.4169	$192.42	$192.40	$192.40
Purchase #4	$236.51	8.125%	$255.7264	$255.73	$255.75	$255.70
Purchase #5	$188.25	4.189%	$196.1358	$196.14	$196.15	$196.10
Purchase #6	$149.26	4.720%	$156.3051	$156.31	$156.30	$156.30
Purchase #7	$14.32	7.676%	$15.4192	$15.42	$15.40	$15.40
7 purchase totals =	$1,021.51		$1,089.9358	$1,089.96	$1,089.95	$1,089.80