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	$195.34	13.165%	$221.0565	$221.06	$221.05	$221.10
Purchase #2	$196.94	10.395%	$217.4119	$217.41	$217.40	$217.40
Purchase #3	$169.35	8.831%	$184.3053	$184.31	$184.30	$184.30
Purchase #4	$206.47	7.296%	$221.5341	$221.53	$221.55	$221.50
Purchase #5	$104.93	4.328%	$109.4714	$109.47	$109.45	$109.50
Purchase #6	$160.80	4.359%	$167.8093	$167.81	$167.80	$167.80
Purchase #7	$108.58	13.671%	$123.424	$123.42	$123.40	$123.40
7 purchase totals =	$1,142.41		$1,245.0125	$1,245.01	$1,244.95	$1,245.00