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	$148.88	6.493%	$158.5468	$158.55	$158.55	$158.50
Purchase #2	$29.60	6.118%	$31.4109	$31.41	$31.40	$31.40
Purchase #3	$169.29	3.610%	$175.4014	$175.40	$175.40	$175.40
Purchase #4	$137.66	10.587%	$152.2341	$152.23	$152.25	$152.20
Purchase #5	$105.59	9.868%	$116.0096	$116.01	$116.00	$116.00
Purchase #6	$227.47	9.808%	$249.7803	$249.78	$249.80	$249.80
Purchase #7	$185.58	5.222%	$195.271	$195.27	$195.25	$195.30
7 purchase totals =	$1,004.07		$1,078.6541	$1,078.65	$1,078.65	$1,078.60