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	$107.31	4.268%	$111.89	$111.89	$111.90	$111.90
Purchase #2	$137.39	13.837%	$156.4007	$156.40	$156.40	$156.40
Purchase #3	$71.55	3.627%	$74.1451	$74.15	$74.15	$74.10
Purchase #4	$50.99	7.455%	$54.7913	$54.79	$54.80	$54.80
Purchase #5	$47.52	7.777%	$51.2156	$51.22	$51.20	$51.20
Purchase #6	$246.97	5.867%	$261.4597	$261.46	$261.45	$261.50
Purchase #7	$40.25	12.227%	$45.1714	$45.17	$45.15	$45.20
7 purchase totals =	$701.98		$755.0738	$755.08	$755.05	$755.10