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	$195.32	7.662%	$210.2854	$210.29	$210.30	$210.30
Purchase #2	$167.46	8.849%	$182.2785	$182.28	$182.30	$182.30
Purchase #3	$139.28	3.716%	$144.4556	$144.46	$144.45	$144.50
Purchase #4	$243.85	12.291%	$273.8216	$273.82	$273.80	$273.80
Purchase #5	$145.73	12.278%	$163.6227	$163.62	$163.60	$163.60
Purchase #6	$64.70	3.714%	$67.103	$67.10	$67.10	$67.10
Purchase #7	$179.27	9.583%	$196.4494	$196.45	$196.45	$196.40
7 purchase totals =	$1,135.61		$1,238.0162	$1,238.02	$1,238.00	$1,238.00