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	$57.85	5.535%	$61.052	$61.05	$61.05	$61.10
Purchase #2	$101.33	12.334%	$113.828	$113.83	$113.85	$113.80
Purchase #3	$102.97	10.326%	$113.6027	$113.60	$113.60	$113.60
Purchase #4	$175.97	5.629%	$185.8754	$185.88	$185.90	$185.90
Purchase #5	$137.90	6.187%	$146.4319	$146.43	$146.45	$146.40
Purchase #6	$118.60	11.760%	$132.5474	$132.55	$132.55	$132.50
Purchase #7	$181.31	12.486%	$203.9484	$203.95	$203.95	$203.90
7 purchase totals =	$875.93		$957.2858	$957.29	$957.35	$957.20