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	$85.46	4.791%	$89.5544	$89.55	$89.55	$89.60
Purchase #2	$45.65	10.827%	$50.5925	$50.59	$50.60	$50.60
Purchase #3	$107.64	6.154%	$114.2642	$114.26	$114.25	$114.30
Purchase #4	$225.56	8.636%	$245.0394	$245.04	$245.05	$245.00
Purchase #5	$131.71	6.502%	$140.2738	$140.27	$140.25	$140.30
Purchase #6	$217.89	13.545%	$247.4032	$247.40	$247.40	$247.40
Purchase #7	$71.43	9.576%	$78.2701	$78.27	$78.25	$78.30
7 purchase totals =	$885.34		$965.3976	$965.38	$965.35	$965.50