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	$148.57	3.416%	$153.6452	$153.65	$153.65	$153.60
Purchase #2	$47.55	9.407%	$52.023	$52.02	$52.00	$52.00
Purchase #3	$100.58	4.260%	$104.8647	$104.86	$104.85	$104.90
Purchase #4	$31.55	3.329%	$32.6003	$32.60	$32.60	$32.60
Purchase #5	$71.35	4.149%	$74.3103	$74.31	$74.30	$74.30
Purchase #6	$40.30	7.856%	$43.466	$43.47	$43.45	$43.50
Purchase #7	$38.48	10.366%	$42.4688	$42.47	$42.45	$42.50
7 purchase totals =	$478.38		$503.3783	$503.38	$503.30	$503.40