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	$199.39	8.162%	$215.6642	$215.66	$215.65	$215.70
Purchase #2	$52.81	7.739%	$56.897	$56.90	$56.90	$56.90
Purchase #3	$224.84	9.666%	$246.573	$246.57	$246.55	$246.60
Purchase #4	$56.71	5.699%	$59.9419	$59.94	$59.95	$59.90
Purchase #5	$233.82	12.402%	$262.8184	$262.82	$262.80	$262.80
Purchase #6	$69.72	7.717%	$75.1003	$75.10	$75.10	$75.10
Purchase #7	$173.73	5.290%	$182.9203	$182.92	$182.90	$182.90
7 purchase totals =	$1,011.02		$1,099.9151	$1,099.91	$1,099.85	$1,099.90