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	$194.55	5.669%	$205.579	$205.58	$205.60	$205.60
Purchase #2	$53.88	12.770%	$60.7605	$60.76	$60.75	$60.80
Purchase #3	$40.79	6.873%	$43.5935	$43.59	$43.60	$43.60
Purchase #4	$234.90	12.763%	$264.8803	$264.88	$264.90	$264.90
Purchase #5	$94.51	5.659%	$99.8583	$99.86	$99.85	$99.90
Purchase #6	$6.68	12.484%	$7.5139	$7.51	$7.50	$7.50
Purchase #7	$91.83	13.137%	$103.8937	$103.89	$103.90	$103.90
7 purchase totals =	$717.14		$786.0792	$786.07	$786.10	$786.20