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	$129.39	12.121%	$145.0734	$145.07	$145.05	$145.10
Purchase #2	$19.78	9.383%	$21.636	$21.64	$21.65	$21.60
Purchase #3	$108.29	13.609%	$123.0272	$123.03	$123.05	$123.00
Purchase #4	$181.87	13.742%	$206.8626	$206.86	$206.85	$206.90
Purchase #5	$119.56	5.797%	$126.4909	$126.49	$126.50	$126.50
Purchase #6	$43.61	13.485%	$49.4908	$49.49	$49.50	$49.50
Purchase #7	$105.78	6.701%	$112.8683	$112.87	$112.85	$112.90
7 purchase totals =	$708.28		$785.4492	$785.45	$785.45	$785.50