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	$53.43	11.445%	$59.5451	$59.55	$59.55	$59.50
Purchase #2	$211.49	10.221%	$233.1064	$233.11	$233.10	$233.10
Purchase #3	$176.93	8.583%	$192.1159	$192.12	$192.10	$192.10
Purchase #4	$134.39	5.856%	$142.2599	$142.26	$142.25	$142.30
Purchase #5	$159.67	12.856%	$180.1972	$180.20	$180.20	$180.20
Purchase #6	$105.95	8.866%	$115.3435	$115.34	$115.35	$115.30
Purchase #7	$115.26	10.421%	$127.2712	$127.27	$127.25	$127.30
7 purchase totals =	$957.12		$1,049.8392	$1,049.85	$1,049.80	$1,049.80