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	$53.38	11.367%	$59.4477	$59.45	$59.45	$59.40
Purchase #2	$22.52	3.871%	$23.3917	$23.39	$23.40	$23.40
Purchase #3	$231.60	13.453%	$262.7571	$262.76	$262.75	$262.80
Purchase #4	$238.74	4.488%	$249.4547	$249.45	$249.45	$249.50
Purchase #5	$187.73	11.758%	$209.8033	$209.80	$209.80	$209.80
Purchase #6	$82.55	4.292%	$86.093	$86.09	$86.10	$86.10
Purchase #7	$241.58	3.718%	$250.5619	$250.56	$250.55	$250.60
7 purchase totals =	$1,058.10		$1,141.5094	$1,141.50	$1,141.50	$1,141.60