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	$207.31	8.314%	$224.5458	$224.55	$224.55	$224.50
Purchase #2	$183.77	4.212%	$191.5104	$191.51	$191.50	$191.50
Purchase #3	$228.40	11.563%	$254.8099	$254.81	$254.80	$254.80
Purchase #4	$82.28	9.861%	$90.3936	$90.39	$90.40	$90.40
Purchase #5	$144.27	11.152%	$160.359	$160.36	$160.35	$160.40
Purchase #6	$138.78	9.539%	$152.0182	$152.02	$152.00	$152.00
Purchase #7	$174.82	13.463%	$198.356	$198.36	$198.35	$198.40
7 purchase totals =	$1,159.63		$1,271.9929	$1,272.00	$1,271.95	$1,272.00