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	$173.25	13.655%	$196.9073	$196.91	$196.90	$196.90
Purchase #2	$37.68	9.531%	$41.2713	$41.27	$41.25	$41.30
Purchase #3	$68.56	10.677%	$75.8802	$75.88	$75.90	$75.90
Purchase #4	$203.82	10.213%	$224.6361	$224.64	$224.65	$224.60
Purchase #5	$100.30	13.531%	$113.8716	$113.87	$113.85	$113.90
Purchase #6	$145.80	12.510%	$164.0396	$164.04	$164.05	$164.00
Purchase #7	$122.63	12.385%	$137.8177	$137.82	$137.80	$137.80
7 purchase totals =	$852.04		$954.4238	$954.43	$954.40	$954.40