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	$117.25	9.389%	$128.2586	$128.26	$128.25	$128.30
Purchase #2	$170.26	8.801%	$185.2446	$185.24	$185.25	$185.20
Purchase #3	$196.81	13.375%	$223.1333	$223.13	$223.15	$223.10
Purchase #4	$50.43	10.268%	$55.6082	$55.61	$55.60	$55.60
Purchase #5	$178.36	3.121%	$183.9266	$183.93	$183.95	$183.90
Purchase #6	$176.66	10.299%	$194.8542	$194.85	$194.85	$194.90
Purchase #7	$101.71	5.145%	$106.943	$106.94	$106.95	$106.90
7 purchase totals =	$991.48		$1,077.9685	$1,077.96	$1,078.00	$1,077.90