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	$120.38	5.455%	$126.9467	$126.95	$126.95	$126.90
Purchase #2	$38.68	7.533%	$41.5938	$41.59	$41.60	$41.60
Purchase #3	$12.83	12.283%	$14.4059	$14.41	$14.40	$14.40
Purchase #4	$148.53	13.404%	$168.439	$168.44	$168.45	$168.40
Purchase #5	$95.99	5.405%	$101.1783	$101.18	$101.20	$101.20
Purchase #6	$80.29	12.635%	$90.4346	$90.43	$90.45	$90.40
Purchase #7	$53.64	11.161%	$59.6268	$59.63	$59.65	$59.60
7 purchase totals =	$550.34		$602.6251	$602.63	$602.70	$602.50