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	$154.93	11.714%	$173.0785	$173.08	$173.10	$173.10
Purchase #2	$153.96	11.688%	$171.9548	$171.95	$171.95	$172.00
Purchase #3	$241.71	3.390%	$249.904	$249.90	$249.90	$249.90
Purchase #4	$52.97	11.638%	$59.1346	$59.13	$59.15	$59.10
Purchase #5	$154.44	12.595%	$173.8917	$173.89	$173.90	$173.90
Purchase #6	$171.34	9.304%	$187.2815	$187.28	$187.30	$187.30
Purchase #7	$81.27	8.718%	$88.3551	$88.36	$88.35	$88.40
7 purchase totals =	$1,010.62		$1,103.6002	$1,103.59	$1,103.65	$1,103.70