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	$131.49	10.763%	$145.6423	$145.64	$145.65	$145.60
Purchase #2	$195.75	10.543%	$216.3879	$216.39	$216.40	$216.40
Purchase #3	$238.60	7.393%	$256.2397	$256.24	$256.25	$256.20
Purchase #4	$167.25	10.380%	$184.6106	$184.61	$184.60	$184.60
Purchase #5	$153.39	7.285%	$164.5645	$164.56	$164.55	$164.60
Purchase #6	$117.75	11.709%	$131.5373	$131.54	$131.55	$131.50
Purchase #7	$30.54	4.137%	$31.8034	$31.80	$31.80	$31.80
7 purchase totals =	$1,034.77		$1,130.7857	$1,130.78	$1,130.80	$1,130.70