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	$66.47	9.143%	$72.5474	$72.55	$72.55	$72.50
Purchase #2	$100.40	5.598%	$106.0204	$106.02	$106.00	$106.00
Purchase #3	$176.58	6.409%	$187.897	$187.90	$187.90	$187.90
Purchase #4	$76.32	8.126%	$82.5218	$82.52	$82.50	$82.50
Purchase #5	$37.38	13.377%	$42.3803	$42.38	$42.40	$42.40
Purchase #6	$80.96	12.731%	$91.267	$91.27	$91.25	$91.30
Purchase #7	$221.37	11.551%	$246.9404	$246.94	$246.95	$246.90
7 purchase totals =	$759.48		$829.5743	$829.58	$829.55	$829.50