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	$186.54	5.390%	$196.5945	$196.59	$196.60	$196.60
Purchase #2	$244.28	7.446%	$262.4691	$262.47	$262.45	$262.50
Purchase #3	$35.39	8.791%	$38.5011	$38.50	$38.50	$38.50
Purchase #4	$149.36	10.385%	$164.871	$164.87	$164.85	$164.90
Purchase #5	$124.93	13.704%	$142.0504	$142.05	$142.05	$142.10
Purchase #6	$65.55	8.603%	$71.1893	$71.19	$71.20	$71.20
Purchase #7	$105.46	9.425%	$115.3996	$115.40	$115.40	$115.40
7 purchase totals =	$911.51		$991.0750	$991.07	$991.05	$991.20