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	$92.89	6.510%	$98.9371	$98.94	$98.95	$98.90
Purchase #2	$188.62	10.284%	$208.0177	$208.02	$208.00	$208.00
Purchase #3	$48.28	6.463%	$51.4003	$51.40	$51.40	$51.40
Purchase #4	$182.41	8.687%	$198.256	$198.26	$198.25	$198.30
Purchase #5	$57.60	3.308%	$59.5054	$59.51	$59.50	$59.50
Purchase #6	$156.29	11.395%	$174.0992	$174.10	$174.10	$174.10
Purchase #7	$63.94	12.381%	$71.8564	$71.86	$71.85	$71.90
7 purchase totals =	$790.03		$862.0721	$862.09	$862.05	$862.10