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	$52.80	12.575%	$59.4396	$59.44	$59.45	$59.40
Purchase #2	$94.34	13.752%	$107.3136	$107.31	$107.30	$107.30
Purchase #3	$63.64	11.128%	$70.7219	$70.72	$70.70	$70.70
Purchase #4	$45.58	6.302%	$48.4525	$48.45	$48.45	$48.50
Purchase #5	$81.78	10.770%	$90.5877	$90.59	$90.60	$90.60
Purchase #6	$6.63	9.119%	$7.2346	$7.23	$7.25	$7.20
Purchase #7	$75.65	3.212%	$78.0799	$78.08	$78.10	$78.10
7 purchase totals =	$420.42		$461.8298	$461.82	$461.85	$461.80