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	$14.69	5.441%	$15.4893	$15.49	$15.50	$15.50
Purchase #2	$56.33	9.172%	$61.4966	$61.50	$61.50	$61.50
Purchase #3	$109.39	11.150%	$121.587	$121.59	$121.60	$121.60
Purchase #4	$113.55	9.689%	$124.5519	$124.55	$124.55	$124.60
Purchase #5	$114.94	7.343%	$123.38	$123.38	$123.40	$123.40
Purchase #6	$71.29	12.741%	$80.3731	$80.37	$80.35	$80.40
Purchase #7	$216.42	5.128%	$227.518	$227.52	$227.50	$227.50
7 purchase totals =	$696.61		$754.3959	$754.40	$754.40	$754.50