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	$167.60	8.520%	$181.8795	$181.88	$181.90	$181.90
Purchase #2	$56.72	10.676%	$62.7754	$62.78	$62.80	$62.80
Purchase #3	$167.45	10.426%	$184.9083	$184.91	$184.90	$184.90
Purchase #4	$102.56	10.165%	$112.9852	$112.99	$113.00	$113.00
Purchase #5	$246.61	10.469%	$272.4276	$272.43	$272.45	$272.40
Purchase #6	$148.99	5.339%	$156.9446	$156.94	$156.95	$156.90
Purchase #7	$30.71	5.231%	$32.3164	$32.32	$32.30	$32.30
7 purchase totals =	$920.64		$1,004.2370	$1,004.25	$1,004.30	$1,004.20