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	$43.86	13.439%	$49.7543	$49.75	$49.75	$49.80
Purchase #2	$88.73	11.471%	$98.9082	$98.91	$98.90	$98.90
Purchase #3	$186.89	4.771%	$195.8065	$195.81	$195.80	$195.80
Purchase #4	$107.51	3.730%	$111.5201	$111.52	$111.50	$111.50
Purchase #5	$209.69	9.249%	$229.0842	$229.08	$229.10	$229.10
Purchase #6	$71.37	9.652%	$78.2586	$78.26	$78.25	$78.30
Purchase #7	$93.76	7.368%	$100.6682	$100.67	$100.65	$100.70
7 purchase totals =	$801.81		$864.0001	$864.00	$863.95	$864.10