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	$199.57	11.436%	$222.3928	$222.39	$222.40	$222.40
Purchase #2	$169.85	3.228%	$175.3328	$175.33	$175.35	$175.30
Purchase #3	$235.42	13.163%	$266.4083	$266.41	$266.40	$266.40
Purchase #4	$107.74	8.164%	$116.5359	$116.54	$116.55	$116.50
Purchase #5	$31.59	4.633%	$33.0536	$33.05	$33.05	$33.10
Purchase #6	$167.94	10.677%	$185.871	$185.87	$185.85	$185.90
Purchase #7	$231.88	4.284%	$241.8137	$241.81	$241.80	$241.80
7 purchase totals =	$1,143.99		$1,241.4081	$1,241.40	$1,241.40	$1,241.40