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	$99.32	13.336%	$112.5653	$112.57	$112.55	$112.60
Purchase #2	$107.88	4.650%	$112.8964	$112.90	$112.90	$112.90
Purchase #3	$232.64	9.572%	$254.9083	$254.91	$254.90	$254.90
Purchase #4	$173.59	12.330%	$194.9936	$194.99	$195.00	$195.00
Purchase #5	$18.97	8.388%	$20.5612	$20.56	$20.55	$20.60
Purchase #6	$89.58	12.291%	$100.5903	$100.59	$100.60	$100.60
Purchase #7	$181.44	10.167%	$199.887	$199.89	$199.90	$199.90
7 purchase totals =	$903.42		$996.4021	$996.41	$996.40	$996.50