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	$150.89	6.583%	$160.8231	$160.82	$160.80	$160.80
Purchase #2	$10.44	9.410%	$11.4224	$11.42	$11.40	$11.40
Purchase #3	$99.74	13.567%	$113.2717	$113.27	$113.25	$113.30
Purchase #4	$243.94	7.635%	$262.5648	$262.56	$262.55	$262.60
Purchase #5	$189.59	3.763%	$196.7243	$196.72	$196.70	$196.70
Purchase #6	$116.57	12.808%	$131.5003	$131.50	$131.50	$131.50
Purchase #7	$10.38	8.575%	$11.2701	$11.27	$11.25	$11.30
7 purchase totals =	$821.55		$887.5767	$887.56	$887.45	$887.60