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	$155.25	4.232%	$161.8202	$161.82	$161.80	$161.80
Purchase #2	$196.64	5.111%	$206.6903	$206.69	$206.70	$206.70
Purchase #3	$186.47	3.818%	$193.5894	$193.59	$193.60	$193.60
Purchase #4	$172.82	9.680%	$189.549	$189.55	$189.55	$189.50
Purchase #5	$212.68	3.191%	$219.4666	$219.47	$219.45	$219.50
Purchase #6	$54.28	10.352%	$59.8991	$59.90	$59.90	$59.90
Purchase #7	$71.26	13.357%	$80.7782	$80.78	$80.80	$80.80
7 purchase totals =	$1,049.40		$1,111.7928	$1,111.80	$1,111.80	$1,111.80