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	$125.40	5.668%	$132.5077	$132.51	$132.50	$132.50
Purchase #2	$204.46	10.813%	$226.5683	$226.57	$226.55	$226.60
Purchase #3	$198.42	9.837%	$217.9386	$217.94	$217.95	$217.90
Purchase #4	$67.82	5.369%	$71.4613	$71.46	$71.45	$71.50
Purchase #5	$137.54	13.131%	$155.6004	$155.60	$155.60	$155.60
Purchase #6	$134.28	13.799%	$152.8093	$152.81	$152.80	$152.80
Purchase #7	$112.33	4.573%	$117.4669	$117.47	$117.45	$117.50
7 purchase totals =	$980.25		$1,074.3525	$1,074.36	$1,074.30	$1,074.40