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	$172.90	8.660%	$187.8731	$187.87	$187.85	$187.90
Purchase #2	$229.50	13.658%	$260.8451	$260.85	$260.85	$260.80
Purchase #3	$64.77	4.759%	$67.8524	$67.85	$67.85	$67.90
Purchase #4	$134.52	8.112%	$145.4323	$145.43	$145.45	$145.40
Purchase #5	$233.25	5.829%	$246.8461	$246.85	$246.85	$246.80
Purchase #6	$60.88	9.375%	$66.5875	$66.59	$66.60	$66.60
Purchase #7	$159.25	9.338%	$174.1208	$174.12	$174.10	$174.10
7 purchase totals =	$1,055.07		$1,149.5573	$1,149.56	$1,149.55	$1,149.50