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	$141.88	9.202%	$154.9358	$154.94	$154.95	$154.90
Purchase #2	$162.88	13.534%	$184.9242	$184.92	$184.90	$184.90
Purchase #3	$103.57	7.225%	$111.0529	$111.05	$111.05	$111.10
Purchase #4	$207.42	7.189%	$222.3314	$222.33	$222.35	$222.30
Purchase #5	$244.67	9.496%	$267.9039	$267.90	$267.90	$267.90
Purchase #6	$40.36	3.378%	$41.7234	$41.72	$41.70	$41.70
Purchase #7	$135.79	6.760%	$144.9694	$144.97	$144.95	$145.00
7 purchase totals =	$1,036.57		$1,127.8410	$1,127.83	$1,127.80	$1,127.80