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	$181.25	8.396%	$196.4678	$196.47	$196.45	$196.50
Purchase #2	$99.95	11.380%	$111.3243	$111.32	$111.30	$111.30
Purchase #3	$90.90	5.702%	$96.0831	$96.08	$96.10	$96.10
Purchase #4	$37.51	6.721%	$40.031	$40.03	$40.05	$40.00
Purchase #5	$192.69	7.684%	$207.4963	$207.50	$207.50	$207.50
Purchase #6	$167.95	8.180%	$181.6883	$181.69	$181.70	$181.70
Purchase #7	$234.72	10.851%	$260.1895	$260.19	$260.20	$260.20
7 purchase totals =	$1,004.97		$1,093.2803	$1,093.28	$1,093.30	$1,093.30