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	$118.60	7.454%	$127.4404	$127.44	$127.45	$127.40
Purchase #2	$61.67	8.667%	$67.0149	$67.01	$67.00	$67.00
Purchase #3	$246.95	9.497%	$270.4028	$270.40	$270.40	$270.40
Purchase #4	$46.59	12.477%	$52.403	$52.40	$52.40	$52.40
Purchase #5	$159.84	4.766%	$167.458	$167.46	$167.45	$167.50
Purchase #6	$127.87	4.671%	$133.8428	$133.84	$133.85	$133.80
Purchase #7	$21.39	12.429%	$24.0486	$24.05	$24.05	$24.00
7 purchase totals =	$782.91		$842.6105	$842.60	$842.60	$842.50