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	$245.87	5.807%	$260.1477	$260.15	$260.15	$260.10
Purchase #2	$84.93	6.462%	$90.4182	$90.42	$90.40	$90.40
Purchase #3	$87.41	13.320%	$99.053	$99.05	$99.05	$99.10
Purchase #4	$218.97	10.564%	$242.102	$242.10	$242.10	$242.10
Purchase #5	$50.37	7.416%	$54.1054	$54.11	$54.10	$54.10
Purchase #6	$30.41	13.346%	$34.4685	$34.47	$34.45	$34.50
Purchase #7	$153.61	4.504%	$160.5286	$160.53	$160.55	$160.50
7 purchase totals =	$871.57		$940.8234	$940.83	$940.80	$940.80