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	$59.40	5.654%	$62.7585	$62.76	$62.75	$62.80
Purchase #2	$100.69	9.736%	$110.4932	$110.49	$110.50	$110.50
Purchase #3	$145.30	6.396%	$154.5934	$154.59	$154.60	$154.60
Purchase #4	$47.47	8.286%	$51.4034	$51.40	$51.40	$51.40
Purchase #5	$105.69	5.455%	$111.4554	$111.46	$111.45	$111.50
Purchase #6	$195.49	9.270%	$213.6119	$213.61	$213.60	$213.60
Purchase #7	$194.50	13.542%	$220.8392	$220.84	$220.85	$220.80
7 purchase totals =	$848.54		$925.1550	$925.15	$925.15	$925.20