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	$41.62	5.235%	$43.7988	$43.80	$43.80	$43.80
Purchase #2	$35.65	3.428%	$36.8721	$36.87	$36.85	$36.90
Purchase #3	$19.36	5.835%	$20.4897	$20.49	$20.50	$20.50
Purchase #4	$247.83	13.327%	$280.8583	$280.86	$280.85	$280.90
Purchase #5	$185.32	7.543%	$199.2987	$199.30	$199.30	$199.30
Purchase #6	$231.93	11.643%	$258.9336	$258.93	$258.95	$258.90
Purchase #7	$65.54	10.419%	$72.3686	$72.37	$72.35	$72.40
7 purchase totals =	$827.25		$912.6198	$912.62	$912.60	$912.70