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	$53.58	11.356%	$59.6645	$59.66	$59.65	$59.70
Purchase #2	$9.64	13.475%	$10.939	$10.94	$10.95	$10.90
Purchase #3	$131.82	11.429%	$146.8857	$146.89	$146.90	$146.90
Purchase #4	$204.43	5.632%	$215.9435	$215.94	$215.95	$215.90
Purchase #5	$192.71	9.735%	$211.4703	$211.47	$211.45	$211.50
Purchase #6	$43.49	6.781%	$46.4391	$46.44	$46.45	$46.40
Purchase #7	$133.97	7.765%	$144.3728	$144.37	$144.35	$144.40
7 purchase totals =	$769.64		$835.7149	$835.71	$835.70	$835.70