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	$23.91	8.851%	$26.0263	$26.03	$26.05	$26.00
Purchase #2	$57.99	11.145%	$64.453	$64.45	$64.45	$64.50
Purchase #3	$53.40	5.555%	$56.3664	$56.37	$56.35	$56.40
Purchase #4	$28.31	12.139%	$31.7466	$31.75	$31.75	$31.70
Purchase #5	$74.92	4.807%	$78.5214	$78.52	$78.50	$78.50
Purchase #6	$16.29	11.446%	$18.1546	$18.15	$18.15	$18.20
Purchase #7	$133.61	8.189%	$144.5513	$144.55	$144.55	$144.60
7 purchase totals =	$388.43		$419.8196	$419.82	$419.80	$419.90