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	$45.55	5.154%	$47.8976	$47.90	$47.90	$47.90
Purchase #2	$10.94	5.687%	$11.5622	$11.56	$11.55	$11.60
Purchase #3	$83.74	3.636%	$86.7848	$86.78	$86.80	$86.80
Purchase #4	$109.65	3.607%	$113.6051	$113.61	$113.60	$113.60
Purchase #5	$235.64	6.353%	$250.6102	$250.61	$250.60	$250.60
Purchase #6	$11.98	7.397%	$12.8662	$12.87	$12.85	$12.90
Purchase #7	$94.99	9.150%	$103.6816	$103.68	$103.70	$103.70
7 purchase totals =	$592.49		$627.0077	$627.01	$627.00	$627.10