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	$112.93	13.217%	$127.856	$127.86	$127.85	$127.90
Purchase #2	$61.34	6.580%	$65.3762	$65.38	$65.40	$65.40
Purchase #3	$25.26	10.349%	$27.8742	$27.87	$27.85	$27.90
Purchase #4	$224.99	9.115%	$245.4978	$245.50	$245.50	$245.50
Purchase #5	$148.38	12.473%	$166.8874	$166.89	$166.90	$166.90
Purchase #6	$24.27	9.552%	$26.5883	$26.59	$26.60	$26.60
Purchase #7	$112.33	9.796%	$123.3338	$123.33	$123.35	$123.30
7 purchase totals =	$709.50		$783.4137	$783.42	$783.45	$783.50