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	$228.37	13.303%	$258.7501	$258.75	$258.75	$258.80
Purchase #2	$62.92	9.482%	$68.8861	$68.89	$68.90	$68.90
Purchase #3	$80.82	11.357%	$89.9987	$90.00	$90.00	$90.00
Purchase #4	$241.45	3.473%	$249.8356	$249.84	$249.85	$249.80
Purchase #5	$243.50	3.685%	$252.473	$252.47	$252.45	$252.50
Purchase #6	$126.88	11.767%	$141.81	$141.81	$141.80	$141.80
Purchase #7	$103.89	8.197%	$112.4059	$112.41	$112.40	$112.40
7 purchase totals =	$1,087.83		$1,174.1594	$1,174.17	$1,174.15	$1,174.20