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	$175.37	5.542%	$185.089	$185.09	$185.10	$185.10
Purchase #2	$51.59	3.214%	$53.2481	$53.25	$53.25	$53.20
Purchase #3	$246.72	9.476%	$270.0992	$270.10	$270.10	$270.10
Purchase #4	$200.38	4.131%	$208.6577	$208.66	$208.65	$208.70
Purchase #5	$12.55	3.609%	$13.0029	$13.00	$13.00	$13.00
Purchase #6	$38.48	12.436%	$43.2654	$43.27	$43.25	$43.30
Purchase #7	$127.34	13.540%	$144.5818	$144.58	$144.60	$144.60
7 purchase totals =	$852.43		$917.9441	$917.95	$917.95	$918.00