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	$170.39	3.777%	$176.8256	$176.83	$176.85	$176.80
Purchase #2	$43.29	9.793%	$47.5294	$47.53	$47.55	$47.50
Purchase #3	$153.63	4.425%	$160.4281	$160.43	$160.45	$160.40
Purchase #4	$63.38	13.209%	$71.7519	$71.75	$71.75	$71.80
Purchase #5	$159.86	8.535%	$173.5041	$173.50	$173.50	$173.50
Purchase #6	$137.38	3.644%	$142.3861	$142.39	$142.40	$142.40
Purchase #7	$159.57	12.679%	$179.8019	$179.80	$179.80	$179.80
7 purchase totals =	$887.50		$952.2271	$952.23	$952.30	$952.20