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	$141.96	7.666%	$152.8427	$152.84	$152.85	$152.80
Purchase #2	$228.40	13.112%	$258.3478	$258.35	$258.35	$258.30
Purchase #3	$123.64	7.321%	$132.6917	$132.69	$132.70	$132.70
Purchase #4	$107.97	5.429%	$113.8317	$113.83	$113.85	$113.80
Purchase #5	$61.66	12.136%	$69.1431	$69.14	$69.15	$69.10
Purchase #6	$73.95	11.526%	$82.4735	$82.47	$82.45	$82.50
Purchase #7	$235.65	9.742%	$258.607	$258.61	$258.60	$258.60
7 purchase totals =	$973.23		$1,067.9375	$1,067.93	$1,067.95	$1,067.80