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	$208.43	5.552%	$220.002	$220.00	$220.00	$220.00
Purchase #2	$196.47	13.221%	$222.4453	$222.45	$222.45	$222.40
Purchase #3	$40.47	3.714%	$41.9731	$41.97	$41.95	$42.00
Purchase #4	$164.39	10.460%	$181.5852	$181.59	$181.60	$181.60
Purchase #5	$80.99	10.574%	$89.5539	$89.55	$89.55	$89.60
Purchase #6	$95.95	10.578%	$106.0996	$106.10	$106.10	$106.10
Purchase #7	$148.57	9.533%	$162.7332	$162.73	$162.75	$162.70
7 purchase totals =	$935.27		$1,024.3923	$1,024.39	$1,024.40	$1,024.40