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	$250.66	6.246%	$266.3162	$266.32	$266.30	$266.30
Purchase #2	$154.71	13.416%	$175.4659	$175.47	$175.45	$175.50
Purchase #3	$160.78	5.313%	$169.3222	$169.32	$169.30	$169.30
Purchase #4	$61.42	13.730%	$69.853	$69.85	$69.85	$69.90
Purchase #5	$80.69	12.607%	$90.8626	$90.86	$90.85	$90.90
Purchase #6	$56.65	5.808%	$59.9402	$59.94	$59.95	$59.90
Purchase #7	$208.56	10.461%	$230.3775	$230.38	$230.40	$230.40
7 purchase totals =	$973.47		$1,062.1376	$1,062.14	$1,062.10	$1,062.20