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	$49.40	9.546%	$54.1157	$54.12	$54.10	$54.10
Purchase #2	$150.89	10.411%	$166.5992	$166.60	$166.60	$166.60
Purchase #3	$183.80	7.107%	$196.8627	$196.86	$196.85	$196.90
Purchase #4	$163.32	9.866%	$179.4332	$179.43	$179.45	$179.40
Purchase #5	$171.43	10.604%	$189.6084	$189.61	$189.60	$189.60
Purchase #6	$191.72	8.731%	$208.4591	$208.46	$208.45	$208.50
Purchase #7	$76.86	5.415%	$81.022	$81.02	$81.00	$81.00
7 purchase totals =	$987.42		$1,076.1003	$1,076.10	$1,076.05	$1,076.10