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	$187.49	9.131%	$204.6097	$204.61	$204.60	$204.60
Purchase #2	$249.83	5.147%	$262.6888	$262.69	$262.70	$262.70
Purchase #3	$231.45	10.645%	$256.0879	$256.09	$256.10	$256.10
Purchase #4	$41.77	8.334%	$45.2511	$45.25	$45.25	$45.30
Purchase #5	$54.64	11.386%	$60.8613	$60.86	$60.85	$60.90
Purchase #6	$187.89	4.815%	$196.9369	$196.94	$196.95	$196.90
Purchase #7	$179.35	3.102%	$184.9134	$184.91	$184.90	$184.90
7 purchase totals =	$1,132.42		$1,211.3491	$1,211.35	$1,211.35	$1,211.40