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	$54.54	4.417%	$56.949	$56.95	$56.95	$56.90
Purchase #2	$161.70	3.664%	$167.6247	$167.62	$167.60	$167.60
Purchase #3	$220.30	9.364%	$240.9289	$240.93	$240.95	$240.90
Purchase #4	$137.47	10.233%	$151.5373	$151.54	$151.55	$151.50
Purchase #5	$198.53	11.109%	$220.5847	$220.58	$220.60	$220.60
Purchase #6	$147.87	4.558%	$154.6099	$154.61	$154.60	$154.60
Purchase #7	$85.57	5.701%	$90.4483	$90.45	$90.45	$90.40
7 purchase totals =	$1,005.98		$1,082.6828	$1,082.68	$1,082.70	$1,082.50