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	$132.51	8.567%	$143.8621	$143.86	$143.85	$143.90
Purchase #2	$25.64	7.335%	$27.5207	$27.52	$27.50	$27.50
Purchase #3	$207.57	12.404%	$233.317	$233.32	$233.30	$233.30
Purchase #4	$138.57	4.254%	$144.4648	$144.46	$144.45	$144.50
Purchase #5	$158.32	3.781%	$164.3061	$164.31	$164.30	$164.30
Purchase #6	$55.75	11.115%	$61.9466	$61.95	$61.95	$61.90
Purchase #7	$146.25	6.815%	$156.2169	$156.22	$156.20	$156.20
7 purchase totals =	$864.61		$931.6342	$931.64	$931.55	$931.60