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	$148.64	5.363%	$156.6116	$156.61	$156.60	$156.60
Purchase #2	$142.43	8.721%	$154.8513	$154.85	$154.85	$154.90
Purchase #3	$19.29	4.194%	$20.099	$20.10	$20.10	$20.10
Purchase #4	$161.77	13.696%	$183.926	$183.93	$183.95	$183.90
Purchase #5	$112.29	9.629%	$123.1024	$123.10	$123.10	$123.10
Purchase #6	$145.45	7.278%	$156.0359	$156.04	$156.05	$156.00
Purchase #7	$150.67	6.776%	$160.8794	$160.88	$160.90	$160.90
7 purchase totals =	$880.54		$955.5056	$955.51	$955.55	$955.50