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	$199.57	13.519%	$226.5499	$226.55	$226.55	$226.50
Purchase #2	$135.78	9.370%	$148.5026	$148.50	$148.50	$148.50
Purchase #3	$46.87	3.189%	$48.3647	$48.36	$48.35	$48.40
Purchase #4	$102.51	13.476%	$116.3242	$116.32	$116.30	$116.30
Purchase #5	$111.70	3.747%	$115.8854	$115.89	$115.90	$115.90
Purchase #6	$90.96	13.776%	$103.4906	$103.49	$103.50	$103.50
Purchase #7	$155.56	9.130%	$169.7626	$169.76	$169.75	$169.80
7 purchase totals =	$842.95		$928.8800	$928.87	$928.85	$928.90