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	$131.61	3.681%	$136.4546	$136.45	$136.45	$136.50
Purchase #2	$118.31	9.367%	$129.3921	$129.39	$129.40	$129.40
Purchase #3	$78.87	3.675%	$81.7685	$81.77	$81.75	$81.80
Purchase #4	$231.38	7.413%	$248.5322	$248.53	$248.55	$248.50
Purchase #5	$146.38	8.492%	$158.8106	$158.81	$158.80	$158.80
Purchase #6	$55.47	6.831%	$59.2592	$59.26	$59.25	$59.30
Purchase #7	$93.86	7.443%	$100.846	$100.85	$100.85	$100.80
7 purchase totals =	$855.88		$915.0632	$915.06	$915.05	$915.10