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	$145.82	7.545%	$156.8221	$156.82	$156.80	$156.80
Purchase #2	$249.28	10.202%	$274.7115	$274.71	$274.70	$274.70
Purchase #3	$205.78	7.226%	$220.6497	$220.65	$220.65	$220.60
Purchase #4	$218.33	5.249%	$229.7901	$229.79	$229.80	$229.80
Purchase #5	$5.80	11.337%	$6.4575	$6.46	$6.45	$6.50
Purchase #6	$114.77	10.527%	$126.8518	$126.85	$126.85	$126.90
Purchase #7	$86.50	3.826%	$89.8095	$89.81	$89.80	$89.80
7 purchase totals =	$1,026.28		$1,105.0922	$1,105.09	$1,105.05	$1,105.10