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	$40.78	7.284%	$43.7504	$43.75	$43.75	$43.80
Purchase #2	$97.81	13.584%	$111.0965	$111.10	$111.10	$111.10
Purchase #3	$171.27	13.408%	$194.2339	$194.23	$194.25	$194.20
Purchase #4	$91.35	7.632%	$98.3218	$98.32	$98.30	$98.30
Purchase #5	$116.38	13.317%	$131.8783	$131.88	$131.90	$131.90
Purchase #6	$240.99	10.578%	$266.4819	$266.48	$266.50	$266.50
Purchase #7	$57.94	11.615%	$64.6697	$64.67	$64.65	$64.70
7 purchase totals =	$816.52		$910.4325	$910.43	$910.45	$910.50