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	$160.28	13.483%	$181.8906	$181.89	$181.90	$181.90
Purchase #2	$37.59	9.162%	$41.034	$41.03	$41.05	$41.00
Purchase #3	$19.99	12.605%	$22.5097	$22.51	$22.50	$22.50
Purchase #4	$78.89	4.741%	$82.6302	$82.63	$82.65	$82.60
Purchase #5	$95.28	8.475%	$103.355	$103.36	$103.35	$103.40
Purchase #6	$14.99	3.817%	$15.5622	$15.56	$15.55	$15.60
Purchase #7	$226.43	10.110%	$249.3221	$249.32	$249.30	$249.30
7 purchase totals =	$633.45		$696.3038	$696.30	$696.30	$696.30